Motor vehicle

ABSTRACT

A clutch touch point control system for an automatically actuated clutch includes a determination method of comparing a torque load on the engine and a torque output from the clutch. A correction of the point of engagement is performed when the two values of torque differ by a predetermined amount. The determination of the torque values is averaged over a relatively long period of time in order to reduce the effect of temporary changes due to heating of the clutch linings, etc.

The invention relates to a motor vehicle with a driving unit and atransmission, as well as with an automated torque transmitting system.

In motor vehicles of the above outlined character, the condition ofengagement, or the setting, of the torque transmitting system (e.g., aclutch) or the torque which can be transmitted by the torquetransmitting system is regulated and/or selected by a control unit andan adjusting or setting member; for example, a clutch can be actuated bya hydraulic system with a master cylinder and a slave cylinder as wellas with an electric motor for the initiation of an actuation of theclutch. Such motor vehicles are known, for example, from the publishedGerman patent application No. 40 11 850.

For numerous modes of actuation of the torque transmitting system, it isadvantageous (a) to know the desired clutch torque which has beenselected in dependency on the distance covered by the means foractuating or adjusting the clutch and/or (b) to be in a position torelatively accurately select the torque which can be transmitted by thetorque transmitting system. For example, a disengaging bearing can beutilized to set the torque transmitting system between a fullydisengaged position or condition and a fully engaged position orcondition. A play or idling distance or path exists between the fullydisengaged position of the clutch and a position of engagement, calledthe "engagement" point or "gripping" point, when the torque transmittingsystem begins to transmit torque. As a rule, a progressively increasingtransmission of torque takes place, as a function of the actuating pathor movement of the clutch actuating means, such as a bearing, startingfrom the engagement point and terminating when the clutch is fullyengaged. The engagement point denotes a condition of engagement of theclutch when the clutch begins to transmit torque or, alternatively, theengagement point can be defined as a position.

The knowledge or ascertainment of the engagement point is of utmostimportance because the engagement point of a torque transmitting system,such as a clutch, characterizes that position of engagement or thatextent of movement of the clutch engaging/disengaging means at which thetransmission of torque begins, e.g., as a result of frictionalengagement. If the characteristic curve of the clutch is known, and ifthe engagement point is also known, one can be said to have basically afull knowledge of the entire clutch characteristic.

In the course of its useful life and/or during the interval of actualuse, the operation of a torque transmitting system such as, for example,a friction clutch, which is operated by a control unit and an adjustingmember for the clutch, is subject to fluctuations which can have anumber of different reasons or causes. For example, one reason for ashifting of the engagement point which actually exists in the clutch canbe the increasing wear upon the component parts of the clutch, whichwear takes place during the useful life of the clutch. An example ofthis type of wear would be the wear upon the friction linings. Thechanges which might develop or arise under such circumstances, such asin response to wear, settling phenomena or other change-causingprocesses, are changes which develop over relatively long periods andare of long duration. In addition, there can also develop relativelyshort-lasting fluctuations involving parts of the torque transmittingsystem, and the average duration of such relatively short-lastingchanges can be in the range of from one or more seconds up to one ormore hours. An example of a cause of short-lasting changes is theheating of component parts and the resulting thermal expansion of suchcomponent parts; these changes, too, can cause a shift in the positionof the engagement point of the torque transmitting system.

An object underlying the invention is to provide a motor vehicle with anautomatic torque transmitting system of the above outlined characterwhich exhibits an improved or more satisfactory operational reliabilityand can be operated in a manner which does not cause discomfort to theoccupant(s) of the vehicle.

Another object of the invention is to detect time-dependent changes inthe entire torque transmitting system and to utilize a planned actuationor operation of the torque transmitting system, rather than having toresort to an expensive mechanical solution to the problem of avoiding orreducing the effect of undesirable influences of such changes. A furtherobject of the invention is to provide a motor vehicle which employs anautomated clutch capable of being actuated or controlled in anintelligent manner in order to at least reduce, or to completely avoidor eliminate, undesirable effects which are attributable to a shiftingof the engagement point, such undesirable effects including for examplea jerky movement during setting of the vehicle in motion or aninsufficient acceleration of the motor vehicle or an abrupt excessiveacceleration of the vehicle.

A further object of the invention is to provide a method of controllingor regulating the operation of a torque transmitting system which isutilized in a motor vehicle, the method being of such a nature that itpermits a functionally reliable and comfortable operation of the motorvehicle.

In accordance with the invention, this is accomplished in motor vehiclesof the type having a driving unit and a transmission in that thetransmission of torque which can be transmitted by an automated torquetransmitting system--such as a friction clutch--which may be, but is notrequired to be, installed in the path of torque transmission between thedriving unit and the transmission, is controlled or regulated by acontrol unit. For example, the torque which can be transmitted by thetorque transmitting system can be selected or set by at least oneactuating member which can be operated by the control unit. For example,the positions or conditions of adjustment of the torque transmittingsystem can include a position such as a position of engagement.

It can also be advantageous or desirable to construct a motor vehicle ofthe type having a driving unit, a transmission and an automated torquetransmitting system, as well as a control unit which controls orregulates the torque adapted to be transmitted by the torquetransmitting system, in such a way that the torque which can betransmitted can be set or selected by way of, for example, a position,such as a position of engagement, by means of an actuating, setting oradjusting member which is actuatable by the control unit. The controlunit can detect or ascertain and/or store in memory an engagement pointof the torque transmitting system, at least in one operating point. Theengagement point characterizes a position or condition of engagement atwhich the transmission of torque basically begins.

The stages of operation constitute different operating points of themotor vehicle, and such operating points are distinguishable from eachother on the basis of vehicle parameters.

In accordance with a further advantageous embodiment of the invention,it can be advantageous or desirable if an automated torque transmittingsystem is designed in such a way that its engagement point is adapted atleast in one operating point.

Moreover, it can be advantageous to further develop an embodiment of theinvention in such a way that the engagement point of the torquetransmitting system can be adapted in at least one operating point inthat a stored value of the engagement point can be utilized or processedby the control unit to at least approximate, conform to or equal anactual or real physical value of the engagement point.

The value (signal) which is stored by the control unit as a valuedenoting the engagement point and which is thereupon treated by thecontrol unit as a value being representative of the engagement pointduring setting or adjustment of the clutch, need not be that value whichhas been determined as the engagement point because the value denotingthe engagement point, such as the value of the physical (actual)engagement point can be filtered, etc. Furthermore, the value which isstored as the engagement point can be a value which deviates from theascertained value of the engagement point and can be determined as avalue corresponding to that of the last stored engagement point plus adifferential amount. Thus, one should distinguish between an actuallyexisting engagement point and a value of the engagement point which isused by the control unit to actuate the torque transmitting system. Theactual and stored values of the engagement point can be different, i.e.,they need not necessarily be the same.

It is advantageous if the value of the physical engagement point, suchas a position or condition of engagement of the torque transmittingsystem when the transmission of torque begins is directly or indirectlydeterminable or deducible on the basis of measurements or calculations.

It can also be advantageous if a position or condition of engagement isidentified by the control unit as an engagement point and, basically,the value of the thus determined position of engagement is stored as thevalue of the engagement point.

It is also advantageous if the value which is stored as an engagementpoint stems or originates from a value which has been determined as anengagement point, and it can be of further advantage if the stored valueis derived from a mathematical operation, such as for example addition,from the value which has been determined as an engagement point. Forexample, the increment/decrement for the adaptation of the engagementpoint can be derived, among others, from the actually ascertainedoperating point.

It is also advantageous or desirable if the value which is stored as anengagement point is ascertainable on the basis of at least one value ofthe clutch torque which can be transmitted in at least one preselectableposition of engagement.

Moreover, it can be advantageous or desirable when the value of a clutchtorque which can be transmitted by the torque transmitting system and/ora difference between such values can be ascertained on the basis of atleast one value of engine torque and/or on the basis of a differencebetween engine torques.

Still further, it can be advantageous or desirable if, in accordancewith a novel concept presented herein, a motor vehicle is equipped witha driving unit, a transmission, and an automated torque transmittingsystem, such as a friction clutch, which may be, but is not required tobe, in the path of torque transmission between the driving unit and thetransmission, and if the torque which is adapted to be transmitted bythe torque transmitting system is regulated through a position ofengagement by means of a control unit, which unit controls at least oneadjusting or actuating member of the clutch, in such a way that theengagement point of the torque transmitting system is adapted at leastat one operating point.

Furthermore, it can be advantageous if a motor vehicle is equipped witha driving unit, a transmission, a torque transmitting system--such as afriction clutch--which may be, but is not required to be, in the path oftorque transmission between the driving unit and the transmission, andwith a control unit which is in a signal-receiving connection with atleast one sensor and regulates or controls the torque adapted to betransmitted by the torque transmitting system in dependency upon theoperating point and/or as a function of time. The engagementpoint--which denotes the position of engagement when the transmission oftorque begins--is adapted in such a way that at least one set of data,which pertains to the engagement point, and which is utilized by thecontrol unit and stored in at least one memory is caused to at leastapproximate, at least stepwise, the at least one physically prevailingengagement point.

In accordance with a further inventive concept, it can be advantageousor desirable in a motor vehicle of the type having a driving unit, atransmission, an automated torque transmitting system, such as afriction clutch, which may be, but is not required to be, disposed inthe path of torque transmission, and at least one control unit as wellas at least one actuating member which is actuatable by the control unitand which serves to select the torque capable of being transmitted bythe torque transmitting system in such a way that the torque which iscapable of being transmitted by the torque transmitting system can beset to be anywhere between a value corresponding to full disengagementof the clutch (when the torque capable of being transmitted is zero) andfull engagement of the clutch in which the transmissible torque rises toa maximum value, if the physically existing engagement point, whichpoint characterizes the position or condition of engagement when thetransmission of torque begins, is compared to an intentional actuationeffected by the control unit as a function of time and/or as a functionof the operating point with at least one set of data pertaining to theengagement point and being stored in a memory and the set of data isadapted, at least in a stepwise fashion, when the physical engagementpoint deviates from the set of data pertaining to the stored engagementpoint.

It is further advisable to design a novel embodiment of a motor vehicleof the type having a driving unit, a transmission, an automated torquetransmitting system--such as a friction clutch--which may be, but is notrequired to be, in the path of torque transmission, and at least onecontrol unit as well as at least one actuating member which isactuatable by the control unit and serves to select the torque capableof being transmitted by the torque transmitting system in such a waythat the torque which is capable of being transmitted by the torquetransmitting system can be selected to be anywhere between a valuecorresponding to full disengagement of the clutch (when the torquecapable of being transmitted is zero) and full engagement of the clutchin which the transmissible torque rises to a maximum value, in such away that one carries out at least one of the following adaptations ofthe engagement-point:

an adaptation of the engagement point attributable to long-lastingchanges in the power train or in the torque transmitting system such as,for example, the wear upon the friction linings

an adaptation of the engagement point due to short-lasting changes ofthe engagement point due to short-lasting changes in the power train orin the torque transmitting system, such as for example thermalfluctuations of the torque transmitting system.

It can be of advantage if the engagement point is adapted by resortingto an intentional adjustment or actuation of the torque transmittingsystem and a detection or ascertainment of magnitudes in several steps.

It is of advantage if, in at least one of the selected or completedsteps, there is adopted a measured value which at least represents theengine torque.

It can equally be of advantage if, in at least one of the selected orcompleted steps, there is carried out a setting of the clutch positionwith a predeterminable desired clutch torque, the setting of the clutchbeing determined with the preselectable desired clutch torque byresorting to a stored characteristic curve of the clutch and to thestored value of the engagement point.

It can also be advantageous or desirable if, in at least two of theselected or completed steps, such as in between measurements, oneascertains measured values which at least represent or approximate theengine torque, and at least one further step involves a setting of aclutch position or condition with a preselectable desired or requiredclutch torque and the desired clutch torque is ascertained, selected ordetermined by resorting to a stored characteristic curve of the clutchand to the stored value of the engagement point.

It can be advantageous when such measured values are utilized to formaverage values of data per measurement interval and if at least oneother step involves carrying out a selection of the condition of theclutch with a corresponding desired clutch torque.

An embodiment can be advantageously selected in such a way that the atleast two measurement intervals take place at different positions of theclutch or at different clutch torques.

It is advantageous to select an embodiment in such a way that the atleast two measured values or magnitudes are determined or ascertained atdifferently selected clutch positions or conditions or at differentpreselectable clutch torques.

It can be of advantage if the measured values or magnitudes during thetwo measurement intervals are determined or calculated in differentpositions of the clutch or at different clutch torques, i.e., that themeasured values are determined at different desired or required clutchtorques. For example, the measured values or magnitudes can constitutevalues denoting the engine torque or values which denote or representsuch engine torque.

It can be advantageous if average values of data are determined orcalculated per measuring interval by resorting to the aforementioneddata, such as measured values or magnitudes.

It can also be advantageous if the engagement point of the torquetransmitting system is ascertained or calculated by resort to at leastone measured value of a magnitude denoting the engine torque, at leastat one selected position of the clutch or at a desired clutch torque.

It can also be advantageous or desirable that the ascertained value ofthe engagement point be compared with a stored value of an engagementpoint.

It is also of advantage if a further embodiment of the inventionprovides that the ascertained value of the engagement point be comparedwith a stored value of an engagement point and, when a detectable,predetermined or given difference exists between the two values, thestored value is altered.

Furthermore, it might be desirable that the stored value be changed atleast in such a way that the stored value at least approximates theascertained value.

In accordance with a further inventive concept, it can be advantageousif the stored value is changed at least in such a way that the storedvalue is caused to approach the ascertained value at least in a stepwisefashion with steps of predetermined length.

It can be advantageous if the stored value is caused to come nearer tothe ascertained value with steps of preselectable length, the length ofthe steps being preselectable or having a functional relationship withthe divergence.

It can be of equal advantage when the selection of the clutch torque byway of the control unit in at least one operating point is carried outin such a way that:

a) the clutch torque is selected for a preselectable clutch position orat a preselectable desired clutch torque

b) a first phase involves determining measured values of a parameterwhich denotes the engine torque and, if necessary or desired, anaveraging of the thus determined values,

c) a second phase involves the setting of a preselectable clutchposition or of a preselectable desired clutch torque,

d) a third phase involves the ascertaining of the measured values of aparameter representing the engine torque and, if necessary or desired,an averaging of the value,

e) carrying out a comparison at least between those values of the stepsa) and c) which denote the engine torque and the values of the desiredclutch torque, and

f) altering the stored engagement point in dependency upon the above.

Still further, it might be advantageous--in accordance with a novelconcept presented herein--if the selection or setting of the clutchtorque for the purpose of ascertaining the engagement point and/or forthe purpose of adapting the engagement point by way of the control unitin at least one operating point is carried out in such a way that:

a) the clutch torque is selected in a preselectable set clutch positionor at a preselectable set desired clutch torque, which is determinableon the basis of the stored value of the engagement point and acharacteristic curve of the clutch,

b) measured values of a magnitude denoting the engine torque aredetermined within a preselectable time window and, if necessary ordesired, such measured values are averaged,

c) a further phase involves the setting of a further preselectableclutch position or a further preselectable clutch torque,

d) a further phase or stage involves the ascertaining of measured valuesof a magnitude representing the engine torque, such measured valuesbeing averaged if desired or necessary,

e) one carries out a comparison at least between those values of thesteps b) and d) which denote or represent an engine torque and thevalues of the desired clutch torque as ascertained in the steps a) andc),

f) one carries out an evaluation whether a deviation between at leastone engine torque and at least one desired clutch torque exceeds apreselectable threshold value, and

g) if necessary, the stored engagement point is altered in dependencyupon the comparison or in dependency upon the deviation.

It can be advantageous if the setting of the clutch torque by way of thecontrol unit in at least one operating point is carried out in such away that:

a) the clutch torque is selected for a preselectable position of theclutch or at a preselectable desired clutch torque

b) a first phase involves the ascertaining of measured values whichdenote a magnitude representing the engine torque, such measured valuesbeing averaged if desired or necessary,

c) a second phase involves the setting of a preselectable position ofthe clutch or of a preselectable desired clutch torque,

d) a third phase involves the determination of measured values denotinga magnitude which represents the engine torque, such measured valuesbeing averaged if desired or necessary,

e) a comparison is carried out at least between those values of thesteps a) and c) which denote the engine torque and the values of thedesired clutch torque, and

f) in the event of a departure of the difference from a preselectabletolerance, the engagement point is altered incrementally/decrementallyand stored, and the procedure is carried out anew from the step a) on.

Still further, it can be advantageous when the setting of the clutchtorque by way of the control unit in at least one operating point iscarried out in such a way that:

a) the clutch torque is selected for a first preselectable position ofthe clutch or at a preselectable desired clutch torque

b) a first stage involves determining measured values of a magnituderepresenting the engine torque and, if necessary or desirable, suchmeasured values are averaged,

c) a second phase involves the setting of a preselectable position ofthe clutch or a preselectable desired clutch torque,

d) a third phase involves ascertaining measured values of a parameterrepresenting the engine torque and, if necessary, such measured valuesare averaged,

e) a comparison is carried out at least between those values of thesteps a) and c) which represent an engine torque and the values of thedesired clutch torque, and

f) the engagement point is altered incrementally/ decrementally in theevent of departure of the difference from a preselected tolerance, thealtered engagement point is stored and the procedure is repeated from c)on but resort may still be had to the data of the steps a) and b).

Furthermore, it can be advantageous if the selection of the clutchtorque by way of the control unit, at least in one operating point, iscarried out in such a way that, in a first phase, one determinesmeasured values of a parameter representing the engine torque and suchmeasured values are averaged, a second phase involves the setting of aclutch torque, a third phase involves the ascertaining and the averagingof measured values denoting a parameter which represents the enginetorque, one carries out a comparison at least between the averagedvalues denoting the engine torque and the values denoting the clutchtorque, and the stored engagement point is altered in dependency uponsuch comparison.

It is of particular advantage if the values, such as measured values,denoting the parameter which represents the engine torque and the valuesdenoting the clutch torques are used to ascertain a difference betweenthe measured values of a parameter denoting the engine torque and if oneascertains the difference between the values of the clutch torque, ifsuch differences are compared and, in the event of lack of equality orin response to the exceeding of a predetermined departure, at least onestored value of the engagement point is altered in accordance with theextent of inequality between the differences or in dependency upon thedeparture.

It can be equally advantageous when, in the event of a lack of identityor in the event of a deviation beyond a predeterminable tolerancebetween the difference of the values denoting an engine torque and thedifference of the clutch torques, the adaptation of the engagement pointtakes place incrementally or decrementally. It can also be of advantageif, in the event of an inequality between the difference of the enginetorques and the difference of the clutch torques, the adaptation of theengagement point is carried out incrementally or decrementally.

In accordance with the inventive concept, it can be advantageous if thedifference of the averaged values is used to ascertain a difference ofthe engine torque and the difference is compared with the difference ofthe values of clutch torque and, in the event of a lack of equality, atleast one stored value of the engagement point is altered in accordancewith the lack of equality.

It is advantageous if the measured values or parameters are ascertainedfor the purpose of determining a magnitude which denotes an enginetorque or for the purpose of determining a difference of a parameterdenoting an engine torque, on the basis of signals which characterizethe actual load upon the engine, such as for example the engine torque,the engine RPM, a signal from the load lever, the position of thethrottle valve, the time of ignition, the ignition angle, the negativepressure in the suction manifold and/or the timing of fuel injection.

Furthermore, it can be advantageous if the setting of the clutch torqueby way of the control unit in at least one operating point is carriedout, in accordance with the engagement point, to select apredeterminable desired clutch torque at a position or setting of theclutch or at a selected clutch torque in such a way that, in a firstphase one determines the measured values of a magnitude denoting theengine torque, wherein such values can be averaged if desired ornecessary, thereafter such values of the engine torque are compared withthe set desired clutch torque and, in the event of a detected differencewhich is greater than a preselectable value, the value of the engagementpoint is incremented or decremented at least in a stepwise fashion and,thereafter, in the event of a detection of an incremented or decrementedvalue of the engagement point, the procedure is repeated until thedeparture or deviation is less than the preselectable value.

It is of particular advantage when the length of the steps of stepwiseincrementation or decrementation of the value of the engagements pointexhibits a preselectable value or is dependent upon (such as apercentage of) the deviation.

It can also be advantageous if, when the clutch is disengaged and thetransmissible torque is about to disappear, one ascertains the enginetorque, thereafter the clutch torque, such as the transmissible clutchtorque, is set to match the value of the engagement point plus a desiredclutch torque and the engine torque is ascertained and, if the value ofa preselectable difference between the engine torque and the clutchtorque is exceeded, the value of the engagement point is increasedstepwise and, after each increase, one ascertains the engine torqueuntil the difference between the engine torque and the clutch torque isless than the preselectable value, and the then available value of theengagement point is stored.

In accordance with a further novel concept, it can be advantageous ifthe stepwise incrementing or decrementing of the value of the engagementpoint is carried out until the ascertained engine torque during twosuccessive steps is once smaller and once larger than the selectedclutch torque, and one of the last two values of the engagement point isstored.

It is of advantage if the stepwise incrementing or decrementing of thevalue of the engagement point is carried out until the engine torquewhich is ascertained during two successive steps is once smaller andonce larger than the selected clutch torque, and at least the two lastvalues of the engagement point are used to determine the physical valueof the engagement point.

In accordance with a further inventive concept, it can be advantageous,too, if the physical value of the engagement point is ascertained byresorting to at least two values, such as the two last values, of theengagement point, for example, by resorting to an averaging procedure.

In accordance with an additional novel concept, it can also beadvantageous if the physical value of the engagement point isascertained by resorting to at least two values, such as the last twovalues, of the engagement point, for example, by resorting to linearregression.

In accordance with a further novel concept, it can also be of advantageif the physical value of the engagement point is ascertained on thebasis of at least two values, such as the last two values, of theengagement point, by resorting for example to interpolation.

In accordance with a further inventive concept, it can also be ofadvantage if the value of the engagement point is ascertained byresorting to a linear or nonlinear regression, such as a quadratic orsecond degree, or other interpolation.

Still further, it is advantageous if "negative torques" are selected forthe determination or adaptation of the engagement point. The expression"negative torques" denotes that, starting from the engagement point, theclutch is set to a position in a direction toward disengagement of theclutch.

It is of advantage if the determination or adaptation of the engagementpoint involves the selection of clutch positions which are locatedbetween a position corresponding to the fully disengaged clutch and theengagement point.

It is equally advantageous if, subsequent to the selection of a"negative torque," i.e., of a clutch condition between the fullydisengaged position and the engagement point, there takes place adetermination of a parameter which is representative of an engine torqueand, when a change of the parameter denoting the engine torque relativeto the setting of the position of the clutch takes place, the value ofthe engagement point is adapted.

It is also advisable if, when selecting a desired clutch torque as thesampling torque, the reaction of the engine torque is detected and, whenthe engine torque exceeds a preselectable threshold value, the clutch isdisengaged and the sampling torque is reduced. Sampling torque isdefined in such a way that one selects or sets a transmissible clutchtorque in order to test (i.e., sample) the reaction of the engine. Thevalue of magnitude of the clutch torque selected to test the reaction ofthe engine torque can be said to constitute a sampling torque or testingtorque. In other words, one carries out a sampling or testing operationinvolving such an engagement of the clutch that a certain torque can betransmitted, and such clutch torque should provoke a reaction of theengine torque.

In accordance with a further inventive concept, it can be advantageous,in a method of regulating or controlling a motor vehicle of the typehaving a driving unit, a transmission, an automated torque transmittingsystem--such as a friction clutch--which may be in the path of torquetransmission, but is not required to be in the path of torquetransmission, and at least one control unit as well as at least oneadjusting or actuating member which is controlled by the control unitand serves to select the torque capable of being transmitted by thetorque transmitting unit, if at least one engagement point which isstored in at least one memory is caused to approximate a physicallyexisting engagement point which characterizes the engaged condition ofthe torque transmitting system, e.g. clutch, when the transmission oftorque begins, and the approximation involves an adjustment of thetorque transmitting system which setting is a function of time and/or ofthe operating point.

Furthermore, it can be advantageous if the adaptation of the engagementpoint is carried out in accordance with a multiple-stage procedure insuch a way that a first step involves a determination of measured valuesand the ascertainment of an averaged engine torque, a second stepinvolves a setting of a clutch torque, a third step involves thedetermination of measured values and an ascertainment of an averagedengine torque, that the averaged values of the engine torques arecompared with data pertaining to the clutch torques to carry out atleast an approximation of the set of data denoting the engagement pointto the physical engagement point and, a further step involves thesetting of the originally existing clutch torque.

It can also be advantageous if the determination of measured values forthe determination of engine torque is carried out on the basis ofsignals denoting the engine torque, the engine RPM, the load lever, theposition of the throttle valve, the timing of fuel injection and/or thetiming of fuel ignition.

It is advantageous, for the adaptation of the engagement point of atorque transmitting system in the power train of a motor vehicle with acontrol unit and an adjusting or actuating member for the torquetransmitting system and with sensors for the determination of measuredvalues if, at least in one operating point, the setting of the clutchinvolves at least some of the following steps:

a) selection of a clutch position in which, basically, no torque isbeing transmitted,

b) setting of a clutch position at which a desired clutch torqueM_(Ksoll) is to be transmitted,

c) ascertaining measured values which represent the engine torque andwhich can be utilized to ascertain the engine torque,

d) averaging of the measured values,

e) establishing a difference between the values of torque and/or themeasured values,

f) a comparison of torque values and/or measured values and/ordifferences,

g) incrementing/decrementing of the at least one stored value for theengagement point.

It can be of advantage if, at least in one operating point, the settingof the clutch for adaptation of the engagement point is carried out inat least four steps involving a step of setting the position of theclutch to a value at which a definite or predetermined torque M_(K1) canbe transmitted, a further step of determining the measured valuesM_(Motor) within a time window ΔT₁ at a constant or unchanging settingof the clutch, such measured values being thereupon averaged orcalculated to M_(M1) which denotes the engine torque, an additional stepof selecting a clutch position at which a predetermined desired clutchtorque M_(K2) is to be transmittable, a further step of receiving themeasured values M_(Motor) within a time window ΔT₂ at a fixed orunchanged position of the clutch and of thereupon averaging orcalculating such measured values to result in M_(M2) which denotes theengine torque, and an additional step of comparing essentially thedifference M_(M2) -M_(M1) of engine torques with the difference M_(K2)-M_(K1) of the desired clutch torques, the stored value of theengagement point GP being incremented/decremented by a value ΔGP whenthe comparing step indicates that M_(M2) -M_(M1) is larger/smaller thanM_(K2) -M_(K1) and the difference eventually exceeds a preselectablethreshold, which may be stored in memory.

It can be advantageous if at least one operating point for theadaptation of the engagement point is realized while the vehicle is at astandstill, the transmission is set into a gear ratio, and the brake isactuated.

It can also be advantageous if the time windows ΔT₁ and ΔT₂ areidentical or of different durations, at least one measured value beingascertained per time window.

Furthermore, it can be advantageous if the duration of the time windowsΔT₁ and ΔT₂ is within the range of 0.1 to 10 seconds, it being preferredto select a duration of 1 to 5 seconds, most preferably 1 to 3 seconds.

It can be advantageous to adapt a long-lasting and a short-lastingengagement point.

It can also be advantageous if the long-range engagement point isadapted in the entire torque transmitting system on the basis ofdeveloping long-range changes.

Furthermore, it can be advantageous if the long-range engagement pointis adapted in special operating points, such as for example in asnifting stage. A snifting stage is a phase during which a hydraulicsystem effects or is capable of effecting a volume equalization orcompensation, for example, as a result of the opening of a valve.

It is also advantageous if the short-lasting engagement point on thebasis of short-lasting reversible or irreversible changes is adaptedwithin the entire system of the torque transmitting system.

It can be of advantage to design an embodiment of the invention in sucha way that the value of the increment or decrement of long-rangeadaptation is less than or equals the value of the short-lastingadaptation.

The invention will be explained in greater detail with reference to thedrawings wherein:

FIG. 1 is a schematic representation of a vehicle,

FIG. 2 is a characteristic curve of torque as a function ofdisengagement distance S;

FIG. 3 is a series of curves of torque as a function of time;

FIG. 4 is a flow chart of torque measurement and engagement pointdetermination,

FIG. 5 is a curve of torque v. time,

FIG. 6 is a curve of torque v. time,

FIG. 7 is a curve of torque v. distance S,

FIG. 8 is a time sequence of signals,

FIG. 9 is a flow chart of torque measurement and engagement pointdetermination,

FIG. 10 is a curve of torque v. distance S,

FIG. 11 is a time sequence of signals,

FIG. 12 is a time sequence of signals, and

FIG. 13a and 14 are flow charts of torque measurement and engagementpoint determination.

FIG. 1 shows a motor vehicle 1, such as for example a passenger car or atruck, with a prime mover 2, such as an internal combustion engine or amotor. Furthermore, the power train of the motor vehicle contains atorque transmitting system 3 and a transmission 4. In this embodiment,the transmitting system 3 is disposed in the path of torque transmissionbetween the prime mover 2 and the transmission 4 so that the torquefurnished by the engine can be transmitted by way of the torquetransmitting system 3 to the transmission 4 and from the output of thetransmission 4 to a driven shaft 5 and/or to a driven axle 6 which isinstalled downstream thereof.

It is noted, however, that this invention also contemplates that thetorque transmitting system 3 need not be disposed in the path of torquetransmission between the prime mover and the transmission as when, forexample, the torque transmitting system is installed downstream of anautomated stepless transmission.

The torque transmitting system 3 constitutes a clutch, such as afriction clutch, and this clutch can constitute an automaticallyadjustable clutch which compensates for wear. The clutch 3 is mounted ona flywheel 25 or constitutes with the flywheel a module, and this clutchcomprises essentially a clutch cover or housing 3d, a diaphragm spring3b, a pressure plate 3a and a clutch disc 3e. In this embodiment, theclutch is actuated by a disengaging bearing 3c and a disengaging fork 20by way of a hydraulic system.

In order to select a torque which can be transmitted by the torquetransmitting system 3, it is also possible to employ hydraulic clutchdisengaging means or to resort to a purely electromechanical orelectromagnetic solution. Such arrangements for setting a clutch areknown, for example, from the field of magnetic powder or magneticparticle clutches.

The illustrated transmission 4 is a manual transmission; however, thistransmission can be replaced with an automated or automatic transmissionsuch as a multirange transmission or an infinitely variable transmissionsuch as a transmission (known as CVT) which employs belts and conicaltorque transmitting components. For example, an automated transmissioncan comprise a shifting roller which can select the gear ratios. It isalso possible to employ a manual transmission with a gear ratio selectorin the form of an actor which initiates and carries out a gear ratioselection and gear ratio shifting operation. The transmission can bedesigned in such a way that shifting into a gear ratio can take placewith or without an interruption of traction.

It is also possible to equip or associate an automatic transmission witha torque transmitting system, such as a clutch and/or friction clutch,which is installed at the output side of the transmission. Furthermore,the torque transmitting system can constitute a starter clutch or atorque converter with a lockup or bypass clutch and/or a safety clutchand/or a reversing wheel set gearing with planned selection of thetransmissible torque. The torque transmitting system 3 comprises aninput side 7 and an output side 8, a selected torque being transmittedfrom the input side 7 to the output side 8.

The torque transmitting system 3 is controlled by a control unit orapparatus 13 which can comprise an actor and regulating electronics. Theactor can consist of a prime mover 12, such as an electric motor, whichacts upon a master cylinder 11 by way of a transmission 21, such as abevel gearing, and a pusher or piston rod 22. The movement of the pusher22 (i.e., of the piston of the master cylinder) is detected by adistance monitoring sensor 14. For example, the distance monitoringsensor 14, such as a clutch movement sensor, can constitute apotentiometer or an inductive sensor or a Hall generator sensor or anoptical sensor. The master cylinder 11 is connected with a slavecylinder 10 by way of a motion transmitting device, such as a hydraulicconduit 9. The slave cylinder 10 can be operatively connected with theclutch disengaging means 20 in such a way that a movement of the outputpart of the slave cylinder actuates the disengaging means 20 in order tocontrol, in a planned manner, the torque which can be transmitted by theclutch 3. Furthermore, the slave cylinder 10 can be designed toconstitute a central clutch disengaging member which can directly orindirectly initiate an adjustment or setting of the torque transmittingsystem 3. The disengaging means 20, which is actuated by the output partof the slave cylinder 10, can carry the disengaging bearing 3c which canserve, for example, as a means for directly actuating or adjusting thefriction clutch 3.

In a torque transmitting system, such as a friction clutch, theselection of the torque which can be transmitted is effected by exertinga controlled pressure upon the clutch disc between the flywheel 25 andthe pressure plate 3a. For example, the position of the disengagingmeans 20 can determine the force with which the pressure plate 3a iscaused to bear upon the friction linings of the clutch disc 3e in aplanned manner; the pressure plate 3a can be caused to move between twoend positions and can be fixed in any selected position between the twoend positions.

One end position corresponds to a fully engaged condition of the clutch3 in which the clutch is capable of transmitting a maximal torque, andthe other end position corresponds to the fully disengaged condition ofthe clutch in which the magnitude of the transmissible torque is zero.The engagement point is located between such end positions; namely itcorresponds to an intermediate position of the pressure plate 3a inwhich the clutch 3 begins to transmit torque.

If the engagement point is considered as a position or condition ofengagement of the clutch in which position or condition the clutchtransmits a predetermine torque (such as 0 Nm or 9 Nm or anothertorque), the engagement point can be said to be fixed. However, thermalstressing and/or the wear upon the friction linings of the clutch discin a friction clutch and/or other reversible or irreversible phenomenaor developments can change the position or condition of engagement,i.e., such phenomenon or phenomena can entail a change of the positionof the engagement point GP. For example, if the hydraulic path (conduit9 in FIG. 1) between the master cylinder 11 and the slave cylinder 10 isheated (i.e., if the temperature of the hydraulic fluid in the conduit 9rises), that value of the engagement point GP which is stored in thememory of the control unit 13 can deviate from the actual or real orphysically present value of the engagement point. The engagement pointGP of the torque transmitting system (such as the clutch 3) can beadapted (i.e., caused to conform to changed circumstances) in at leastone operating point of the vehicle.

It is possible to ascertain the engagement point on the basis, forexample, of a direct local measurement in the clutch or, for example, bymeasuring that force with which the clutch is held in the engagedcondition, as a function of the distance covered by the clutch actuating(adjusting) means. Alternatively, one measures the engine torque independency on the condition of engagement (position) of the clutch, anda reaction of the engine torque to actuation of the clutch can beconsidered as an indication of the momentary setting (extent ofengagement) of the clutch and the engagement point.

In order to select a transmissible torque, for example a torque which isless than the momentarily prevailing engine torque, one an for exampleselect a position of the pressure plate 3a which is disposed somewherebetween the two end positions. However, it is also possible to selecttransmissible clutch torques which exceed the then existing enginetorque by a defined or preselected value.

As a rule, a torque transmitting system--such as a friction clutch--isnormally designed in such a way that the maximum transmissible torqueexceeds the nominal engine torque by a certain factor, especially afactor greater than 1.5. Thus, when the clutch is fully engaged, thereexists or is prevalent an application of excessive pressure because,under most circumstances of operation, the input of the torquetransmitting system does not receive the nominal engine torque. Byresorting to a torque follow-up, i.e., to a planned selection of thetorque which can be transmitted by the torque transmitting system, thetransmissible torque can be caused to conform to the existing enginetorque, and it is possible to select--in a planned manner--a slightoverpressure or a slight underpressure, i.e., the torque which can betransmitted by the torque transmitting system is slightly larger orslightly smaller than the existing engine torque.

Among others, the aforediscussed follow-up of transmissible torqueexhibits the advantage that, basically, the clutch is engaged only to anextent as dictated by the momentarily prevailing engine torque and,therefore, a reaction involving a more pronounced disengagement orengagement of the clutch can be carried out within a shorter interval oftime. A torque follow-up with a slight overpressure permits thetransmission of the momentarily prevailing engine torque and ensures adamping of those fluctuations of torque which exceed the torque adaptedto be transmitted by the torque transmitting system because the torquetransmitting system begins to slip in response to the development ofsuch irregularities of torque.

The torque which can be transmitted by the torque transmitting system,such as a clutch, is controlled or regulated by the control unit 13. Theterm "controlling" is intended to denote herein a procedure withoutfeedback in an open loop. As used herein, the term "regulation" isintended to denote a procedure with feedback in a closed loop. In thecase of a feedback, this involves a feedback of a signal denoting anactual value, and one ascertains the difference between the desired andactual values; if possible, the regulator reduces such difference tozero.

In order to effect a controlling or a regulation of the torquetransmitting system, one employs signals which basically denote orcharacterize the operating condition of the motor vehicle 1 and whichare a function of the prevailing characteristic values of the system.The sensors, which detect and indicate the operational parameters andfurnish corresponding signals, transmit such signals to the control unitor electronic unit 13. This control unit or electronic unit can beconnected with further electronic units, such as for example anelectronic unit of an ABS (automatic braking system) system, anelectronic engine management, an antislip regulation or a transmissioncontrol.

A predetermined position or condition of engagement can be furnished,for example, by a characteristic field or a characteristic curve or byfixed positions which are stored in the control unit 13. Suchpreselection or predetermination is carried out by the programmer of thesoftware for the control unit, and the storing of such programmedinformation entails a fixing of the information. However, it is alsopossible to utilize preselectable values in the form of functions orparameters of the motor vehicle, i.e., they might by variable.

By way of example, the embodiment of FIG. 1 shows a throttle valvesensor 15, an engine RPM sensor 16 and a tachometer sensor 17; all ofthese transmit signals denoting measured values, i.e., data, to thecontrol unit 13. Furthermore, the transmission 4 is provided with anactuating lever 18 which is or which can be provided or connected, forexample, with a sensor or sensor system 19 for recognition and/ordetection of the selected transmission gear ratio. Furthermore, therecan be provided in the region of the transmission 4 a sensor or sensorsystem 23 for the recognition of the actual or momentarily effectivetransmission gear ratio and/or of the intention to shift into aparticular gear ratio. The control unit 13 comprises the gearing 21, thepush rod 22 and the master cylinder 11 as well as the positionmonitoring sensor 14 which directly or indirectly detects the positionof the piston of the master cylinder 11. The torque which can betransmitted by, for example, the setting of the torque transmittingsystem 3 can be ascertained or calculated on the basis of the positionof the piston of the master cylinder 11, namely on the basis of thephysical characteristics and/or characteristic values of the connectionincluding the parts 9, 10, 20. It is possible to provide a clutchcondition detecting sensor directly on or to couple such sensor with theactuating means or, for example, on or with the pressure plate 3a.

The control apparatus or control unit 13 is at least temporarily in asignal receiving connection with the sensors or other attachedelectronic units, and transmits signals to the prime mover 12 (such asan electric motor)--for the purposes of setting the clutch, i.e., ofselecting the transmissible torque in dependency upon the measuredvalues and/or the system input values and/or the signals of theassociated sensors and/or the implemented control or regulatingprocedure. To this end, a control program is implemented in the controlunit 13 in either hardware and/or software. In the case of a drivingtorque which is being applied at an operating point and which has beenascertained or calculated on the basis of system input values, thecontrol unit selects or calculates for the clutch-actuating member asetting position and the electric motor 12 receives and is actuated inresponse to reception of a signal denoting a clutch setting value. Theoperative connection between the master cylinder 11 and the slavecylinder 10, such as the hydraulic conduit 9, causes a displacement ofthe piston in the master cylinder 11 that entails the transmission of amovement to the adjusting or actuating means 20, which may be in theform of disengaging fork 20, so that the clutch is set in accordancewith the characteristics, intensity or amplitude of the signal from thecontrol unit 13.

In the embodiment which is shown in FIG. 1 and which employs a mastercylinder 11 and a slave cylinder 10, there is provided a fluid-operatedapproach which employs the hydraulic conduit 9; however, it is alsopossible to utilize embodiments which operate in a different manner.Such alternate solutions can rely, for example, on a purely mechanicalmode of actuating the clutch, e.g., by way of a linkage or a Bowdenwire.

In order to select and to optimize the desired transmissible torque, itis necessary to possess a detailed and accurate knowledge of the entiresystem. For example, such knowledge of, or familiarity with, the systemcan be arrived at in a relatively satisfactory manner if the operatingpoint of the torque transmitting system is known or ascertainable with arelatively high degree of accuracy or can be caused to follow ratherwell or be adequately adapted to the actual circumstances.

A method for the adaptation of the engagement point can provide adetection of the physically existing engagement point, and such value ofthe engagement point is stored in a memory. The software of the controlmethod utilizes such value for the purposes of regulating the operationof the clutch 3.

A further method of adapting the engagement point can provide that onedetects the physically existing engagement point, and such value iscompared with the momentarily stored value of the engagement point,whereupon the stored value of the engagement point is alteredincrementally or decrementally on the basis of such comparison.

The aforedescribed second method exhibits the advantage that, in theevent of inaccurate or erroneous measurement of the engagement point andthe following adaptive step, the stored engagement point does notdeviate appreciably from the physical engagement point. For example,such erroneous or inaccurate measurements can develop in response toconnection or disconnection of auxiliary devices when such connection ordisconnection takes place within the time interval of detection of thephysically existing engagement point or an adaptation of the engagementpoint. In this manner, the ascertained torque at the engagement pointcan depart to a considerable extent from the actual torque at theengagement point. The turning on or the turning off of an airconditioning system can cause an error at the engagement point in therange of 5 to 100 Nm. The auxiliary pump of the power steering systemcan also cause distortions in the range of 10 Nm.

In the event of wear, in the case of tolerances and other departures orchanges, such as for example thermally induced influences in the entireregion affecting or encompassing the torque transmitting system,including the signal transmitting path and the adjusting or actuatingmember, there can take place a change of the actually transmissibletorque or a change of the engagement point in comparison with the storedvalue, and hence a change of the selected transmissible desired clutchtorque or engagement point so that the sets of data in the at least onememory are not indicative of the conditions prevailing in each operatingpoint. For example, a temperature rise in the space under the hood, i.e.engine space, can lead to a heating of the signal transmitting path (9,10, 11) and to a shifting of the physical position of the engagementpoint which entails a difference between the stored value and the actualvalue of the engagement point. If a setting or adjustment of the torquetransmitting system is to take place under such circumstances, theselected transmissible torque departs considerably from the desired orrequired value.

For example, if the torque transmitting system is set or adjusted insuch a way that a small torque is to entail a creeping movement of thevehicle, there can develop an excessive creeping, or no creeping at allwill take place, depending upon the shifting of the engagement point inthe one or the other direction.

The regulation of a creeping start of a vehicle is a highly sensitiveprocedure when the engagement point is shifted in an electronicallycontrolled clutch because the creeping torque which is required toachieve a creeping movement is relatively small. The values of thecreeping torque are in the range between a few Nm and a times 10 Nmwherein a is a number between one and ten.

At the start of a creeping operation, the clutch of the motor vehicle isengaged up to a desired torque so that the vehicle is set in motion,slowly and gradually, while the load lever is held in the idlingposition and the gas pedal is not depressed. However, if the actualcharacteristic curve of the clutch departs from the characteristic curvewhich is programmed into the controls and/or from the stored data, theclutch is engaged to an insufficient extent or to an excessive extent.Consequently, the vehicle will creep at an insufficient rate or at anexcessive rate. If the clutch is engaged to an excessive extent, thereexists the danger that the engine will be choked whereas; if theengagement of the clutch is insufficient, the creeping is not likely tooccur, i.e., the vehicle will be started or set in motion only inresponse to an actuation of the load lever.

The preceding explanations indicate that a so-called shifting of theengagement point entails a shifting of the actual characteristic curveof the clutch relative to the normal characteristic curve. Thecharacteristic curve which is stored in the software and is actuallyutilized follows the initial progress. An adaptation of the engagementpoint denotes a procedure involving a conformance or approximation ofthe engagement point, which is stored in the software and is actuallyutilized, to the physically prevailing or existing engagement point. Itis particularly advantageous to resort to an adaptation of theengagement point which involves a parameter, signal or structuraladaptation, a parameter adaptation being preferred at this time.

It should be possible to carry out a detection of the engagement pointtaking into account engine parameters, such as for example, shifting ofthe transmission into a gear ratio, the actuation of a brake, the engineRPM, the speed of the motor vehicle, the RPM of the transmission, anon-existing change of the prevailing engine torque (e.g. due to theturning on or off of an air conditioning system), the non-existence ofan intention to shift the transmission into a different gear ratio, theabsence of actuation of the gas pedal and possibly other vehicleparameters. However, the presence of certain parameters can also denotethat the determination of the engagement point should be interrupted orprevented, for example, when the operator of the vehicle intends toshift the transmission into a different gear ratio which should resultin planned (e.g., automatic) disengagement (opening) of the clutch andthe control unit 13 should not initiate a determination of theengagement point of the clutch.

FIG. 2 shows a curve 50 representing the characteristic curve of theclutch and shows torque M measured along the ordinate and thedisengagement distance s of the clutch measured along the abscissa, itbeing assumed here that the clutch is of the type shown in FIG. 1wherein the actuation is carried out by hydraulic means, such as by thecylinders 10, 11 and conduit 9.

In the event of a cooling of the hydraulic fluid in the hydraulic system(9, 10, 11) which is used to adjust the clutch, the characteristic curveof the clutch is shifted from the curve 50 to the curve 51, whereas suchcurve is shifted from 50 to 52 in the event of a rise of the temperatureof hydraulic fluid. In the event of a cooling or a heating of thehydraulic fluid, the torque M_(K11) which is to be selected follows adifferent path, i.e., the position of disengagement of the clutch ischanged so that, when one selects a predetermined value of clutchtorque, it is necessary to select a different distance s, i.e., achanged setting of the clutch in the event of a change of thecircumstances, such as a change in the temperature of the hydraulicfluid.

If one takes into consideration a fixedly selected and set clutchposition, such as can be designated for example as GP, this means thatsuch value corresponds (in the event of a normal characteristic curve ofthe clutch as denoted at 50) to a desired torque of 9 Nm as measuredalong the ordinate of the coordinate diagram shown in FIG. 2. It will beseen that, if the hydraulic fluid is cooled, the selected or set clutchtorque is twice as large, as shown by point 53 in the diagram of FIG. 2.If the temperature of the fluid rises, the selected clutch torque isvery small and is nearly zero, as shown by point 54 in the diagram ofFIG. 2.

As can be seen in the example of FIG. 2, a change of the characteristiccurve of the clutch in comparison with the stored original data denotingthe characteristic curve of the clutch entails a false setting of thetransmissible torque when the distance being covered is the same. Thoughthe description of FIG. 2 was made in connection with distortionsresulting from temperature changes of the hydraulic fluid, analogoussituations will arise for example in the event of wear or otherprocesses or developments which affect or alter the system.

It is to be taken into consideration, in connection with the eventswhich effect a change of the torque transmitting system, that one mustdistinguish between reversible and irreversible events. A wear upon thefriction linings or upon other component parts is an irreversibleprocess. On the other hand, for example, thermally induced changes ofthe torque transmitting system are reversible events which can ariserepeatedly under a number of circumstances such as, for example, afterstoppage of the vehicle or during renewed starting as well as inresponse to changes of load upon the motor vehicle. Such events can varyas a function of time.

FIG. 3 shows curves denoting the values of torque M as a function oftime t, i.e., the time t is measured along the abscissa and the torque Mis measured along the ordinate. Curve 100 denotes the clutch torque, andcurve 101 denotes the engine torque. The signal denoting the enginetorque 101 is ascertained either directly or on the basis of signalswhich are proportional to the engine torque or represent the enginetorque, such as for example the engine RPM, the position of the throttlevalve, the subatmospheric pressure in the suction manifold, and/or theignition time or the position of the load lever. It is also possible torely on a combination of such parameters for the purpose of establishingthe engine torque. At the start of the illustrated time interval in theregion between the instants 102 and 103, the clutch torque is basicallyconstant and has a low value 108, for example zero. Also, the enginetorque is essentially constant; however, inaccuracies of measurement aswell as time-dependent variations due to the regulation of idling causea certain fluctuation or straying of the value denoted by the curve 101.The magnitude of the engine torque within this time interval (betweenthe instants 102 and 103) is shown at 104.

In the time interval between the instants 103 and 105 (interval 106),one ascertains or receives measured values and, upon the expiration ofthis interval, the measured values are averaged so that an averagedmeasured value M_(M1) is available for the time interval 106; suchaveraged value is capable of being stored and denotes the engine torquewithin this interval (106) of time. During the time interval between theinstants 105 and 107, the clutch torque rises from a value 108 to avalue 109, and the value of the engine torque also increases during suchinterval, namely from the value 104 to a value 110. The increase of theengine torque results from the condition of equilibrium during idlingbecause the idling regulator increases the engine torque when the loadupon the engine is increased. Thus, the basic premise is the staticequilibrium torques at the engine, such as normally also develops as aresult of the regulation of idling in conventional engines. Thus, anincrease of the clutch torque when the vehicle is at a standstill willentail a substantially equivalent increase of the engine torque. In viewof the above, the stored value of the engagement point is thenconsidered as having been properly selected or set or stored when astatus of equilibrium is realized at the engine, i.e., when (it beingassumed that the engagement point has been properly ascertained) theengine torque increases by a value which matches or approximates theincrease of the clutch torque. During the interval between the instants107 and 111 (interval 113), the engine torque--or the signalsrepresenting the engine torque--will be detected again and the thusobtained signals are thereupon averaged. Within the interval between theinstants 111 and 112, the clutch torque descends or drops from the value109 back to the value 108. The engine torque also decreases accordingly,back to the value 104.

In order to adapt the engagement point, the averaged value denoting theengine torque within the time interval 106 is compared with the averagedvalue during the time interval 113 in such a way that one establishes,for example, a difference and one ascertains that absolute value whichis indicative of the increase of the averaged engine torque. The extentof the increase of the clutch torque is also known at such time. Thedifference between the clutch torque 109 within the time interval 113and the clutch torque 108 within the time interval 106 furnishes thedesired or required value by which the averaged engine torque shouldhave risen within the corresponding time intervals in order to ensurethat the stored value of the engagement point is correct or that acorrect value of the engagement point has been stored. In the event ofan equilibrium of engine torques during idling, a minor increase of theclutch torque entails an equal rise of the engine torque. If adifference exists between the differences of engine torques and thedifferences of clutch torque, the value of the engagement point wasimproperly selected and stored prior to the cycle or, alternatively, thesystem including (a) the signal transmitting path, (b) the clutch, and(c) the power train, has changed during the interval following the lastadaptation step.

Owing to such change, for example of the signal transmitting means (9,10, 11) or of the torque transmitting system (3), the difference of theaveraged engine torques departs from the difference of the clutchtorques. As a result of such departure or deviation, the stored value GPof the engagement point, as indicated in FIG. 2, is changed to a smallextent in order to come closer to or to match the values of the actualengagement point. Depending upon whether the divergence between thedifference of the averaged values of the engine torque and thedifferences of the values of clutch torque is positive or negative,i.e., depending upon the direction of shifting of the physicalengagement point (see FIG. 2), the stored engagement point GP isincrementally increased or decrementally reduced by a value ΔGP. Theamount of the increment ΔGP can depend upon the difference between thevalues of engine torque and of clutch torque. However, it is alsopossible to select a fixed or unchanging value of ΔGP.

Adaptation of the engagement point is preferably carried out undercertain conditions of operation, namely when it is not noticed or feltor is noticed or felt only slightly by the passengers) and the operatorof the vehicle. One such operating point or range of operation is thestandstill of the vehicle while the prime mover, e.g. engine, isrunning, while the transmission is shifted into a gear ratio, and whilethe brake (be it a manually operated brake, a foot-operated brake or aso-called fixing brake) is actuated. Further possible operatingconditions are those at which a minor change of the transmissible clutchtorque does not entail a change of the condition of the vehicle so thatthe adaptation procedure can be carried out in such a way that it is notnoticed by the operator. However, it is equally possible to carry outthe ascertainment of the operating point under other circumstances ofoperation.

In order to carry out an adaptation, it is first determined whether ornot there exists an operational condition which permits an adaptation ofthe engagement point or of the characteristic curve of the clutch. Ifsuch an inquiry results in a positive answer, an adaptation of theengagement point is carried out, for example, in accordance with theprocedure as illustrated in FIG. 3. The carrying out of the adaptationnecessitates a window in the range of seconds, namely that an adaptationcan be meaningfully carried out within a time window of one second toapproximately 20 seconds. Basically, one prefers to resort to adaptationprocedures which involve resort to time windows within the range of asecond to ascertain the measured values and to complete the averaging ofthe thus ascertained values. The intervals of time windows for thedetermination and averaging of measured values depends upon the clockfrequency of the control unit for the determination of data and upon thequality of the signal which is to be ascertained. The time windows forthe determination of data in the embodiment of FIG. 3 are set up forintervals of two seconds each. The duration of repetition, or theinterval between the adaptation procedures, can be variable; animmediate succession of adaptation procedures (without intervals betweenthem) is generally not advisable. It has been found to be of advantagethat a certain interval of time elapses between successive adaptationprocedures; such interval is required in a majority of motor vehicles toagain stabilize the idling behavior of the engine. The starting of asubsequent adaptation step is preferably carried out only when the powertrain including the engine is again in a state of equilibrium.

As already described above, FIG. 3 shows an adjustment of the torquetransmitting system, such as a clutch, within the time interval startingat the instant 102 and terminating at the instant 112, for the purposeof ascertainment or adaptation. After the instant 112, there follows aninterval 125 during which no adaptation is being carried out. During theinterval 125, there develops a rise of the engine torque, and this isindicated by the arrow 126. Such basically abrupt or sudden rise of thetorque can be caused by an auxiliary device or consumer which was turnedon or off at the instant 127. Such auxiliary consumer can constitute,for example, a dynamo or light generator, an air conditioning system, anauxiliary pump of the power steering unit and/or other aggregate(s) suchas, for example, one or more compressors which can be turned on and off.

During the interval between the instants 127 and 128, the adaptationstrategy is carried out in a manner as described hereinbefore, and theprogress of the adaptation can correspond to that during the intervalbetween the instants 103 and 112.

Due to the establishment of differences and averaging of the data, theaforedescribed spontaneous one-time event or changes of the enginetorque which arise or develop during the intervals including 126 exertno influence at all or their influence is insignificant. If an abruptchange of torque develops outside of the time window for adaptation, thedetermination or adaptation of the engagement point is not distorted.

If a change of the engine torque takes place during the adaptationphase, the averaging of data ensures that the undesirable influence isat least weakened.

The averaging of sets of data which are obtained during the respectivemeasurement periods is of advantage for the quality of the data because,as a rule, it is advisable to take into consideration fluctuations ofthe measured data within a given time window.

The adaptation of the engagement point is preferably effected in such amanner that, upon completion of a determination of the differencebetween the averaged values of the engine torque and the selected clutchtorque within at least two intervals of time, one ascertains orcalculates whether the engine torque(s) is (or are) larger or smallerthan the value(s) of the clutch torque. In the event that the value(s)of the engine torque is (or are) greater than the value(s) of the clutchtorque(s), the engagement point GP which has been stored in the softwareis increased by one increment. If the opposite is the case, i.e., thatthe difference of averaged values of the engine torque is less than thedifference of the clutch torques, an equilibrium of engine torques--atleast during idling--brings about that the actually effective clutchtorque is smaller than the preselected value of the desired clutchtorque, then the engagement point is decremented under the just outlinedcircumstances.

If the operating condition is such that an adaptation is acceptable, theadaptation is carried out at least as a function of time. Anincrementing or decrementing of the engagement point by a value ΔGPensures that the engagement point is not altered by a substantial valuein a single step.

If there arises or develops a distortion of the engine torque, forexample because the equilibrium was disturbed for a short interval oftime or on short notice by an auxiliary consumer, there would develop,in the absence of stepwise incrementation or decrementation, anexcessive change of the engagement point.

The alteration of the engagement point takes place incrementally ordecrementally, i.e., the clutch torque which is set during thenext-following cycle does not have a value GP (see 109 in FIG. 3) butrather a value GP±ΔGP. The positive or negative sign of ΔGP depends uponwhether in the course of the last comparison the difference of theengine torques was larger or smaller than the difference between theclutch torques.

Furthermore, it can be of advantage if, for the purposes of adaptationof the engagement point, one carries out a plurality of measuring cyclesand the engagement point is adapted or calculated or approximated on thebasis of calculated or ascertained measured values obtained during aplurality of cycles.

In order to adapt an engagement point, it can be of advantage to resortto a procedure with a dynamic-ΔGP in contrast to an incremental ordecremental adaptation with fixed adaptation steps ΔGP. The value of ΔGPcan depend upon the calculated physical engagement point, as well asupon the desired clutch torque and can be determined, for example, byutilizing a functional relationship or can be stored in the form of acharacteristic field. The value of ΔGP can depend linearly upon thedeviation between the desired and actual values of the engagement point.

FIG. 4 is a flow chart which can represent, for example, the progress orflow of an adaptation procedure. Proceeding from decisional step 200,the adaptation of the engagement point is initiated or prevented independency upon the occurrence of certain events or as a function oftime. At step 200, the control system determines operating condition onthe basis of system parameters and decides whether or not there existsan operating condition in which the adaptation of the engagement pointcan be carried out or will be carried out, or whether the operatingcondition is such that an adaptation of the engagement point will nottake place.

If at step 200, the event sensing and signal processing control systemdetermines that there exists an operating condition which permits anadaptation of the engagement point, the adaptation of the engagementpoint is carried out in such operating condition as a function of time,namely the adaptation of the engagement point preferably does not takeplace continuously but rather by resorting to time windows within whichan adaptation is carried out.

If at step 200, the control system determines that an adaptation is tobe carried out, step 201 furnishes the interval (Δt) during which themeasured values of the engine torque or the measured values ofparameters which are proportional to the engine torque or at leastbasically denote the engine torque are being received by the controlunit 13.

At step 202, the torque transmitting system 3--such as a frictionclutch--is set for a desired torque value M_(K) =M_(K1), i.e., at thisvalue the clutch can be disengaged, engaged or retain unchanged,depending upon which desired value of clutch torque M_(K) was set priorto such time.

At step 203, M_(Mi) signals are received which denote discrete measuredvalues, namely values which are at least representative of the enginetorque. The measured values are added during the time interval T₁ =n₁ xΔt wherein T₁ and n₁ determine the entire interval of reception ofmeasured values and n₁ basically denotes the number of the ascertainedmeasured values or the number of ascertained measured values plus one,and Δt denotes the clocking frequency of the reception of measuredvalues. Furthermore, the measured values M_(Mi) obtained within the timeinterval T₁ are totalized.

At step 204, the control unit forms an average value of the enginetorque and this value is averaged by the number of the received measuredvalues.

At step 205, the clutch is set for a desired torque M_(K2), i.e., M_(K)=M_(K2). It would be expected that the value of M_(K2) would depart fromthat of M_(K1). At step 206, again the same as with step 203, measuredvalues M_(Mi) within the time interval T₂ which is n₂ x Δt are summed.At step 207, the average value of the engine torque within the timeinterval T₂ is calculated, such averaging involving the ascertainment ofthe median value of the measured values which were obtained within thetime interval T₂.

At the end of step 207, the clutch is again set to a value which is thesame as prior to the start of the adaptation. However, this procedurecan be dispensed with, i.e., the clutch torque can remain at the valueM_(K2).

At step 208, one obtains the difference M_(M2) -M_(M1) of the averagedengine torques and, at the same time, there is ascertained thedifference M_(K2) -M_(K1) between the selected clutch torques.Subsequent to the establishment of such differences, there is carriedout a comparison to ascertain whether the difference between the enginetorques is larger or smaller than the difference between the clutchtorques and, in dependency thereon, a decision is made as to how tochange or adapt the engagement point which was selected by the software.If the difference between the engine torques is larger than thedifference between the clutch torques, the system proceeds to step 209which involves an increase of the engagement point GP by the value ΔGP.Alternatively, i.e., when the difference between the engine torques issmaller than or equals the difference between the clutch torques, thesystem proceeds to step 210 which involves a decrementing of theengagement point GP by the value ΔGP.

The incrementing/decrementing of the value of the engagement point canalso be carried out only when the discrepancy or departure of the enginetorque difference (M_(M2) -M_(M1)), from the clutch torque difference(M_(K2) -M_(K1)) exceeds a predeterminable tolerance range.

If the departure is within the tolerance range, an adaptation or analteration of the stored value of the adaptation point can be dispensedwith. If the departure is outside of the tolerance range, the value ofthe engagement point is incremented or decremented.

The adaptation is completed in the next step, and the event controls ortiming controls denoted by step 200 decide whether or not a furtheradaptation procedure or adaptation step is to be initiated.

An adaptation of that value of the engagement point which is utilized bythe control unit takes place in several steps (stages). For example,when the vehicle is at a standstill, the clutch is engaged, the brake isactuated and the gas pedal is not depressed (i.e., when the engine isidling and the clutch is at least substantially disengaged), the firststep of adapting the engagement point involves a determination of theengine torque. The next step involves such actuation of the clutch thatthe clutch is set to transmit a transmittable desired clutch torque, forexample, 10 Nm. Thus, the position or condition of the clutch is set byresorting to a characteristic curve which is stored in the control unitso that the clutch is ready to transmit a desired torque. Once thesetting of the clutch to transmit a desired torque (such as for example10 Nm) is completed, the engine torque is ascertained again in a furtherstep or during a subsequent measuring interval. The subsequent stepinvolves a comparison of the engine torque, which was ascertained whilethe clutch was disengaged, with the engine torque which was ascertainedwhile the clutch was set to transmit a predetermined torque, or oneestablishes a difference between the two values of engine torque and thesignal denoting such difference is or can be processed. If the increaseof the engine torque in comparison to the increase of the clutch torque(namely from practically zero when the clutch is disengaged to apreselectable value which is furnished by the control unit 13) issmaller, the value of the engagement point which is utilized (stored) bythe control unit is shifted or changed relative to the physicallyexisting or available engagement point. Thus, the determination of theengagement point takes place in several stages or steps, and certainsteps can involve the detection or the measurement (monitoring) of theengine torque, whereas the other steps involve engagement of the clutchto a value which is determined by the control unit. It is also possibleto engage (close) the clutch in a stepwise fashion, and the clutchclosing steps can alternate, for example, with detections of the enginetorque.

The determination as to whether the difference of the engine torques islarger or smaller than the difference of the clutch torques is based onthe premise that, due to the fluctuation of the measured values denotingthe engine torque and of the ensuing averaging of such measured values,it is not always possible to achieve an identity between the valuesdenoting the engine torque and the values denoting the clutch torque,i.e., it is not absolutely necessary to ascertain whether or not anequality or identity actually exists and the ensuing not-carried out orskipped modification of the adaptation of the engagement point can bedispensed with under certain circumstances.

It can be of advantage if negative clutch torques are also determined inconnection with the adaptation of the engagement point. Such negativeclutch torques are ascertained in such a way that one selects a clutchposition and the corresponding clutch torque which is set by actuatingin a direction from the engagement point toward a full disengagement ofthe clutch. If the engagement point denotes a condition of the clutch atthe instant of a start of torque transmission by the clutch, and if anessentially progressive increase of the transmissible torque or clutchtorque takes place when the clutch is actuated in a direction from suchengagement point toward the closed condition, one can refer to negativetorques when the clutch is actuated in a sense from the engagement pointtoward the fully disengaged condition even if the adjustment of theclutch in a direction from the engagement point toward the fullydisengaged position is small or minimal and this results in a reductionto zero of the torque which is being transmitted by the clutch. Thus,under such circumstances, a negative torque does not denote that thedirection of rotation has been changed; "negative torque" indicates aclutch position or condition between the fully disengaged position orcondition and the engagement point. Thus, when a negative torque isselected, the clutch assumes a position or condition between a fullydisengaged position or condition and the engagement point so that it ispossible that, during adaptation of the engagement point, a drag torquewould be transmitted in response to a setting of the clutch to theengagement point which could result in a distortion of the values ofengine torque. By selecting a position between the fully disengagedposition of the clutch and the engagement point, one achieves that it ispossible to measure a value of engine torque at which no drag torque isbeing transmitted by the clutch. The setting or position of the clutchthen serves as a control value or regulating value.

It will be seen that the reference to the selection or setting of anegative clutch torque describes or circumscribes (in a roundabout way)that the clutch is disengaged in such a way that it assumes a disengagedcondition which is between the engagement point and the fully disengagedcondition or that the clutch is caused to assume its completelydisengaged condition.

In accordance with a further novel concept, it can be of advantage ifthe engagement point is ascertained in such a way that the engine torque(y Nm+x Nm) belonging to a particular clutch torque value (0 Nm+x Nm) isascertained in a stepwise fashion.

The above can be achieved in such a way that, in a first step, oneascertains the value (Y Nm) of the engine torque which corresponds to aclutch torque (0 Nm) and one thereupon selects a sampling torque(denoting that torque which is selected for the clutch to test thereaction of the engine) having a value of for example 4 Nm clutchtorque. One then ascertains the reaction of the engine, i.e., themagnitude of the engine torque (Z Nm) transmitted as a reaction toselection of the sampling torque for transmission by the clutch. If thedifference between the engine torques (z Nm-y Nm) is outside of atolerance range of clutch torques (0 Nm-4 Nm), the value of theengagement point does not coincide with the value of the real engagementpoint. The difference or divergence between the differences (z Nm-yNm)-(0 Nm-4 Nm) can be utilized to ascertain the divergence of theengagement point. In the next step, that value of the engagement pointwhich is utilized in the control unit can be incremented or decremented.By the same token, the utilized value of the engagement point can bealtered to match the calculated value of the engagement point. It isfurther possible to carry out a comparison between several values of theclutch torque and the engine torque. For example, let it be assumed thatthe clutch torque is set to a value of (4 Nm) and one detects an enginetorque of (4 Nm+x Nm). If the clutch torque is reduced to (2 Nm), onedetects an engine torque of (2 Nm+x Nm). If the clutch torque is reducedto (0 Nm), one detects an engine torque of (x Nm). In the next step, theclutch can be fully opened and the engine torque can be ascertainedwithout the transmission of a drag torque by the clutch. Thus, the valueof the engagement point can be ascertained and that value of theengagement point which is utilized by the control unit can be caused toconform or to be adapted to the physical value of the engagement point.The engagement point is calculated in such a way that the engine torqueincreases accordingly in response to selection of a given clutch torque.

The above described procedures or methods of ascertaining the engagementpoint and/or of adapting the engagement point or of the stored valuerepresenting the engagement point for utilization in connection with thecontrolling or regulation of the torque transmitting system are based onthe premise that there should exist an equilibrium condition of thestationarily operating engine, i.e., that the applied or selected clutchtorque is compensated for by the idling regulator in that the enginetorque is increased by the value of the clutch torque. For example, thiscan take place when the vehicle is at a standstill, or when the vehicleis rolling while the transmission is set into a gear ratio or when thetransmission is not in gear. In the last instance, one relies on thedrag torque of the transmission. If the novel vehicle is operated in thejust outlined manner, one proceeds from a basically stationary conditionof the engine so that the engine torque cannot be affected by any otherinfluences, i.e., all effects or changes affecting the clutch torque canbe attributed to the selected adjustment of the clutch.

If the condition of the engine is not stationary or is not entirelystationary, such as can take place, for example, during the warming upstage of the engine by idling enrichment or a shifting of the ignitionangle, a knowledge of the existence of the reason for the non-stationarybehavior of the engine, i.e., a knowledge of the source of disturbance,renders it possible to calculate or ascertain the influence of suchsource of disturbance upon the engine torque; for example, one cancalculate or ascertain the development of such source of disturbance asa function of time. For example, when the clutch is fully disengaged,the engine torque can be detected within a given interval of time as afunction of time or as a function of another parameter. Such dependencyof the engine torque, for example, upon time, can be extrapolated by afunction so that such extrapolation is essentially valid and applieswithin a preselectable following interval of time and the engine torquevaries accordingly. Thus, a next-following determination of theengagement point with a setting of a clutch torque and the determinationof the engine torque, for example, subsequent to the above outlinedprocedure, relates to an engine torque which is variable as a functionof time. Those values of the engine torque which correspond to thevalues of clutch torque are ascertained by taking into consideration thebasis of the engine torque which varies as a function of time.Basically, such values of the engine torque are no longer variable withtime as a reaction to a change of the clutch torque but can be resortedto for a determination of the engagement point.

Based on the previously determined progresses of the engine torque as afunction of time or identifications of the timely progress of the enginetorque, one can ascertain a change of the engine torque which is notattributable to the selected clutch torque. In this manner, oneascertains an underlying timely progress of the engine torque. Suchprogress can be relied upon for a determination of the clutch torque.

Based upon the previously ascertained time dependency or time-dependentvariation of the engine torque, for example, based on an engine RPMwhich varies with time, one can thus generate or calculate an enginetorque which is constant in time and is independent of the RPM, and suchengine torque can be utilized as a basis for the determination and/oradaptation of the engagement point.

The coordinate system of FIG. 5 shows the progress of an engine RPMn_(mot) and of an engine torque M_(mot) as a function of time t. At theinstant t_(o), the combustion engine (such as an Otto engine or a Dieselengine or a like engine) is started. The engine RPM 301 and the enginetorque 302 increase from a value which basically equals zero torespective first values following the starting of the engine. Duringsuch phase, an idling enrichment and/or an adjustment of the ignitionangle or other procedures will enhance the starting phase or the warmingup phase of the engine in a manner which is desirable in the event of acold start enrichment. The engine RPM n_(mot) (see the curve 301)initially rises from zero to a value 310 to thereupon undergo a basicdecrease up to the instant t₃ before the engine RPM 301 reaches orassumes its idling value 311 at the instant t₃ if the circumstances arenormal and the engine is warm. Substantially simultaneously with thetime-dependent variation of the RPM 301, namely within the interval fromthe instant t_(o) to the instant t₃, there takes place a modulation ofthe engine torque 302 as a function of time, and the engine torque isbasically constant from the instant t₂ on. The engine torque isavailable as a digital or a digitalized signal, and the signalsfluctuate by a value ΔM. The average value of the engine torque 302 isbasically at the value 312. It is also possible to furnish acorresponding analog signal.

During the interval from t_(o) to t₂, the engine torque can be basicallyapproximated by a linear function 303. If a determination of theengagement point is taking place during such time interval, the function302 can be relied upon as the underlying function and such function canbe resorted to in order to convert the calculated engine torque to abasis which is independent of time.

If this is not carried out, it is possible to wait up to the instant t₃; from there on, the engine torque is unchanged.

FIG. 6 shows a coordinate system which is a modification of that shownin FIG. 3. In this coordinate system, the curve 400 denotes the selectedclutch torque, the curve 401 denotes the engine torque, and the curve402 denotes a calculated function as a function of time. The enginetorque (curve 401) does not represent a stationary signal such as inFIG. 3 but rather a signal which varies with time t. The straight-linecurve 402 corresponds essentially to the time-dependent progress of theengine torque in the absence of load as a result of actuation of theclutch. The absolute value of the function denoted by the curve 402 canbe caused to conform to the actual value of the engine torque. Forexample, the function denoted by the curve 402 can be ascertained on thebasis of a determination of data pertaining to the values of the enginetorque within a preselectable time window. Due to the determination ofthe RPM-dependent signal denoting the engine torque (curve 403), whichis proportional to the function denoted by the curve 402, one canascertain or calculate a signal denoting the engine torques and beingindependent of the RPM. If such signal is available, one can carry out adetermination or adaptation of the engagement point, for example, alsoduring idling enrichment. This can be advantageous, for example, duringstarting of the engine. The function which is denoted by the curve 403basically corresponds to the signal denoted by the curve 401 minus avalue which is proportional to the function denoted by the curve 402.The signal denoted by the curve 403 can be utilized in a manner asalready described with reference to the coordinate system of FIG. 3.

FIG. 7 shows a coordinate system 500 wherein the transmissible clutchtorque M_(K) is shown as a function of the position s of the clutch or afunction of the distance s to be covered by an actuator to actuate theclutch. The position or the distance S_(K) can denote the positions orthe distances covered by the tips of the prongs of a diaphragm spring ina friction clutch or the position or distance covered by a clutchdisengaging or actuating bearing. However the distance or position s canalso denote the distance covered by or the position S_(Gz) of a mobilepart of a fluid-operated master cylinder or the position of or thedistance S_(Nz) covered by a mobile part of a fluid-operated slavecylinder.

In the coordinate system 500 of FIG. 7, the curve 501 denotes thetransmissible clutch torque M_(K) as a function of the distance s. Atthe engagement point Gp 502, the value of the curve 501 drops to zero,i.e., the engagement point is or can be defined as that condition ofengagement of the clutch or that distance covered by a mobile part ofthe clutch, such as the pressure plate of a friction clutch, at whichthe transmission of torque begins. The point 503 denotes that actuatingdistance or that setting of the clutch when the clutch is fullydisengaged. The clutch to which the coordinate system 500 pertains is apush-type clutch, but analogous circumstances will exist in a pull-typeclutch.

When its behavior is fully known, and if its characteristic force linesare also known, the characteristic curve of the clutch can be denoted bya point. For example, such point can constitute the engagement point Gp502 of FIG. 7 or another point, such as for example the point 504 on thecurve 501. For example, if the distance s at a fixed value of thetransmissible clutch torque is known, for example, on the basis of adetermination of the torque, the entire characteristic curve 501 of theclutch can be ascertained as a function of the actuating distance. Ifthe value of the physical engagement point is shifted, for example, dueto a shrinkage or an expansion of a hydraulic fluid in a hydraulicconduit (9) between a master cylinder (11) and a slave cylinder (10),for example, during a measurement of the distance being covered by amobile part of the master cylinder, a recognition of the position or ofthe distance covered at a predetermined value 504 of the clutch torquecan be resorted to for the purpose of causing the characteristic curveof the clutch basically to approximate or to match the actualcircumstances, for example, by resorting to a shifting of thecharacteristic curve along the abscissa.

In accordance with a further inventive procedure or method, it ispossible to ascertain whether or not the value of the engagement pointGp 502 (which is being utilized by the control unit for control orregulation purposes) corresponds to the physical engagement point.Furthermore, it is advisable for the sake of safety to ascertain whetheror not a drag torque is being transmitted at a time when the vehicle isat a standstill, the transmission is shifted into a gear ratio, and theclutch is set at the engagement point 502 or in the position 507 whichcorresponds to the engagement point 502 plus an offset 508. If thatvalue of the engagement point which is utilized by the control unit doesnot match the physical engagement point, one can transmit a drag torqueby setting the clutch at the engagement point 502 or at a value Gp (502)plus the offset. If the transmission is set in neutral, i.e., if no gearratio is being selected, if the clutch is set to the conditioncorresponding to a maximal displacement s, and if the transmission isthereupon shifted into a selected gear ratio and the clutch is set tothe engagement point Gp or to a value Gp+offset, such procedure can beresorted to for the detection whether or not a drag torque is beingtransmitted at the setting Gp, or Gp plus offset, of the clutch.

FIG. 8 shows a coordinate system wherein the curve 550 denotes thedistances covered by the clutch actuating means, the curve 551 denotesthe engine torque, and the curve 552 denotes the engine RPM, all as afunction of time t. The transmission (4) is assumed to be in neutralgear during the interval between the instants t_(o) and t₁, and thetransmission is assumed to have been shifted into a gear other thanneutral gear at the instant t₁ ; from the instant t₁ on, the controlunit (13) regulates the clutch (3) in such a way that it is engaged atleast to a position corresponding to the engagement point Gp or to aposition corresponding to the engagement point Gp plus offset (508 inFIG. 7). The progress of the curve 550 in FIG. 8 indicates that, duringthe interval between t₁ and t₂, the position of the clutch has beenchanged from the value 558 to the value 559. The change of the conditionof the clutch 3 is basically completed at the instant t₂. By measuringor otherwise ascertaining the engine torque M_(mot) (curve 551) and theengine RPM n_(mot) (curve 552), it is possible to ascertain a dragtorque M_(drag) which can develop, for example, in that position of theclutch when the transmission is in gear (other than neutral). The dragtorque corresponds to the difference between the value 561 and the value560, i.e., to the difference between the engine torque while the clutchis partially engaged and the engine torque when the clutch is fullyengaged. The engine RPM (curve 552) decreases in response to thedevelopment of drag torque before the idling regulator counteracts suchreduction of RPM and returns the RPM to its desired or required value.

If a drag torque exists when the condition of the clutch is such that itassumes the engagement point Gp or a position denoted by Gp plus offset,the engagement point which is being relied upon by the control unit doesnot correspond to the actual engagement point because, in such positionsor settings of the clutch, the drag torque should be zero or at aminimum or negligibly small value. The engagement point is adapted if adrag torque develops. The adaptation can be carried out incrementally ordecrementally, in dependency on the magnitude of the drag torque.

It is also possible, for example, in order to eliminate drag torque, tochange the value of the offset (508 in FIG. 7), namely one can increasethe value of the offset.

FIG. 9 is a flow chart of the various steps or stages of thedetermination of the presence or absence of drag torque which wasdiscussed with reference to FIGS. 7 and 8. The procedure is started atstep 600. At step 601, a determination is made by the control unit andon the basis of signals from sensors and system input values, whether ornot the engine is on and whether or not the vehicle is at a standstill.This can be ascertained, for example, on the basis of the engine RPM andthe wheel RPM. If this is the case, i.e., if the engine is on and thevehicle is at a standstill, the system proceeds to step 602;alternatively, the procedure is terminated (note the block 605) withinthe particular interval of time. At step 602, it is determined whetheror not the transmission is in gear or is in neutral. If the transmissionis in a gear other than neutral, the engine torque is ascertained (step603) and the thus obtained value M_(ohne) of the engine torque is storedat step 604; it is preferred to simultaneously store the cycle or thetime of storing the value M_(ohne). The procedure is then terminated atstep 605, within the particular cycle. If the inquiry at step 602indicates that the transmission is in a gear other than neutral, afurther inquiry serves to ascertain whether or not the transmission wasin a gear other than neutral during the preceding cycle. For example,this can be ascertained by addressing a status bit which was not changedas yet during the then prevailing cycle and which can indicate whetheror not the transmission was in a gear other than neutral during thepreceding cycle. If the inquiry indicated that the transmission was inneutral, this indicates that the shifting into a gear other than neutraltook place very recently. If this is the case, at step 606 the clutch isset from basically a fully disengaged condition to the engaged positionGp or Gp plus offset. In either event, no drag torque or no appreciabledrag torque should exist at such time. Next, at step 607 the enginetorque M_(mit) is determined and then stored. Next, at step 608, thedifference between M_(mit) and M_(ohne) is determined. This differenceM_(mit) -M_(ohne) corresponds to the drag torque M_(drag) when thetransmission is in a gear other than neutral. At step 609, thedifference M_(mit) -M_(ohne) =M_(drag) is compared with a thresholdvalue. If the value of the drag torque M_(drag) exceeds such thresholdvalue, the engagement point is adapted (step 610), or the offset isaltered (step 606), particularly increased, so that the existing dragtorque is reduced. The procedure for this particular cycle is terminatedat step 605.

FIG. 10 shows a coordinate system 650 wherein the torque M_(K) which canbe transmitted by the clutch is measured along the ordinate and thedistance s is measured along the abscissa, i.e., the torque M_(K) is afunction of the distance s. The distance s can be that distance which iscovered, for example, by the tips of tongues forming part of a diaphragmspring in a friction clutch and/or the distance covered by a clutchdisengaging member and/or the distance covered by a mobile part of amaster cylinder and/or a distance covered by a mobile part of a slavecylinder. The value of s denotes the actuation or lack of actuation orthe extent of engagement of the clutch. In order to be able to completethe determination of the engagement point as rapidly as possible, and toobtain a reliable value for the position of the engagement point, it isdesirable to select an appropriate starting value for the determinationof the engagement point and to thereupon determine the engagement point,for example, in an iterative manner. In this connection, it can be ofadvantage if, initially, the value of the engagement point isascertained as the anticipated value on the basis of a theoreticallyexpectable, i.e. adapted to be anticipated, characteristic curve. Thecurve 651 of FIG. 10 denotes such a characteristic curve and comprises afirst portion 652 in which, basically, no modulation of M_(K) as afunction of s exists. In a second portion 653, modulation of M_(K) iscarried out as a function of s, i.e., in this portion the torque whichcan be transmitted by the clutch decreases basically monotonously as afunction of s. The value of the clutch actuating distance at 654corresponds to a neutral point at which the transmissible torque nolonger increases in response to further engagement of the clutch. Thus,the engagement point 655 (defined here as the engagement distance at apredetermined transmissible torque, e.g., 9 Nm) denotes a theoreticalengagement point. Such theoretical engagement point Gp corresponds tothe neutral point plus the nominal engagement point 656 which, in turn,denotes the difference between 654 and 655 and thus denotes a distance.

The balance or sum of torques at the engine during unchanging idlingessentially represents the basis for a determination of the engagementpoint. Furthermore, and based on the aforedescribed circumstances, it ispossible to carry out a determination of the engagement point even ifthe idling is not unchanging by taking into consideration the cause ofthe non-constant progress of idling. When the engine is idling in anunchanging manner, the angular momentum or torsion of the engine issimplified if one disregards other consumers such as for example, theair conditioning unit, to an equilibrium between the engine torque andthe clutch torque:

    M.sub.M =M.sub.K

with

    θ.sub.M *dω/dt=0.

The condition of equilibrium indicates that a rise of the clutch torqueM_(K) should effect an equivalent rise of the engine torque. The settingof the engagement point is considered to be correct when a predeterminedchange of the clutch torque M_(K) entails a corresponding rise of theengine torque which has been selected or caused by the engine controls.The engine controls and the detection of the engine torque M_(M) thusbasically serve as a sensor for the selected transmissible clutch torqueM_(K).

FIG. 3 illustrates by way of example a determination of the engagementpoint which involves a determination of the engine torque at twodifferent clutch torques and the difference between the thus obtainedvalues of the engine torque serves for the determination of theengagement point by taking into consideration the selected clutchtorque.

FIG. 11 illustrates a coordinate system wherein time t (in seconds) ismeasured along the abscissa and the torque is measured along theordinate. The curve 701 denotes a selected desired clutch torque whichis determined on the basis of the actually stored value of theengagement point 702, such as is stored by the control unit, as afunction of time t. The clutch torque 701 is a sampling torque which isapplied for the purpose of determining the engagement point.Furthermore, such value of the engagement point 702, which is utilizedby the control unit, is indicated as a function of time. FIG. 11 furthershows, in addition to the aforementioned parameters, a curve 703 whichdenotes the engine torque M_(mot) as a function of time t. As alreadymentioned above, "sampling torque" denotes that selected clutch torquewhich is applied to test the reaction of the engine.

During the time interval between the instants t_(o) and t₁, theengagement point 702 which is utilized by the control unit is set to avalue 710 and is stored. At the instant t₁, one starts with adetermination of the engagement point and, by using the value 710 forthe engagement point, one selects a desired clutch torque of 6 Nm.Starting from the actually utilized value of the engagement point, theclutch is engaged or closed by a precalculated value beyond theengagement point 710 in order to select the desired clutch torqueM_(Ksoll). Thus, the control unit "assumes" that the transmissibletorque amounts to 6 Nm.

As shown in FIG. 11, the detected engine torque, indicated by curve 703,does not assume any detectable value during the interval between theinstants t₁ and t₂. Thus, and based on the preceding equation denotingthe conditions for an equilibrium, the control unit utilizes for theengagement point a value 710 which does not match or correspond to thereal engagement point. At the instant t₂, the control unit reduces thevalue of the utilized engagement point from 710 to 711. Since, at theinstant t₂ or during the interval between t₂ and t₃, the transmissibledesired clutch torque M_(Ksoll) did not change in comparison with thepreviously selected desired clutch torque M_(Ksoll), the change of theutilized value of the engagement point from 710 to 711 denotes that theposition of the clutch or the condition of engagement is being changedin accordance with the newly selected engagement point so that, as aresult, the desired clutch torque will remain essentially unchanged.

During the interval between t₂ and t₃ (it being assumed that 711 denotesthe value of the engagement point as well as that the desired clutchtorque is set at 6 Nm), one ascertains the engine torque. It will beseen that, at t₃, the engine torque assumes a very low value which iswell below the desired clutch torque (6 Nm). Thus, the value 711 of theengagement point is not, as yet, the proper or correct value of thephysical engagement point. Furthermore, the value 711 is not within atolerance range from the correct value for the engagement point. Thus,and since the engagement point shown at 711 departs excessively from thereal engagement point, the control unit decrements the utilized value ofthe engagement point starting at t₃. As can be seen in FIG. 11, thevalue of the engagement point utilized by the control unit is changedfrom 711 to 712 during the interval between the instants t₃ and t₄. Uponcompletion of such decrementing of the engagement point, the desiredclutch torque of 6 Nm is set with the newly fixed value of theengagement point and one ascertains the engine torque (curve 703) duringthe interval between t₃ and t₄. When t=t₄, the engine torque assumes avalue of approximately 2 Nm, i.e., such value is well below the desiredvalue of 6 Nm, which is the magnitude of the desired clutch torque.

Thus, the value 712 of the engagement point is still not the correctvalue, namely the value of the physical engagement point. Furthermore,the value 712 is not within the range of acceptable tolerances (betweenthe engagement point utilized by the control unit and the physicalengagement point). Thus, and since the departure of the engagement pointshown at 712 from the real engagement point is excessive, that value ofthe engagement point which is utilized by the control unit isdecremented again starting at t₄. Thus, the value 713 is selected forthe interval between the time instants t₄ and t₅. Subsequent to suchadaptation, i.e. decrementing or, if necessary, incrementing, of theutilized engagement point, the desired clutch torque of 6 Nm is set withthe newly selected value 713 for the engagement point and the enginetorque (curve 703) is ascertained during the interval from t₄ to t₅. Ascan be seen in the example of FIG. 11, when t=t₅, the engine torqueassumes a value of approximately 4 Nm which, again, is well below thevalue (6 Nm) which would denote an equality of clutch torque and enginetorque.

Thus, the value 713 of the engagement point is still different from thevalue of the physical engagement point. Furthermore, the value 713 isstill outside of an acceptable range of tolerances between the value ofthe engagement point as utilized by the control unit and the value ofthe physical engagement point. Therefore, the value of the engagementpoint (as represented at 713) is decremented (or, if necessary,incremented) at the instant t₅. The thus obtained value 714 is utilizedby the control unit during the interval between t₅ and t₆ to set thedesired clutch torque of 6 Nm, and the value of the engine torque isascertained during the interval between t₅ and t₆. As can be seen inFIG. 11, the value of the engine torque rises to 5.75 Nm which is stillsomewhat less than the desired clutch torque of 6 Nm.

Accordingly, the value 714 of the engagement point which is utilized bythe control unit is still not identical with the value of the physicalengagement point. Furthermore, the value (as shown at 714) is still notwithin an acceptable range of tolerances. Therefore a further adaptation(decrementing or incrementing, depending upon the sign of the deviation)is initiated at t₆ to obtain a new value 715 which is utilized by thecontrol unit in connection with the setting of the desired clutch torqueof 6 Nm. The engine torque (curve 703) is monitored during the intervalbetween t₆ and t₇ ; FIG. 11 shows that the engine torque amounts to 7.5Nm, i.e., for the first time such value is above the desired value (6Nm) of the clutch torque. This indicates that the physical engagementpoint of the clutch is between the values 714 and 715.

In order to decide which value of the engagement point is to be utilizedat least for the first time, the invention provides severalpossibilities, such as:

1. The last ascertained value of the engagement point, namely the value715, is stored and is utilized, at least temporarily, as that value ofthe engagement point which is to be relied upon by the control unit.Thus, such value (715) is that utilized value at which, for the firsttime, there develops a change in the sign, i.e. between positive andnegative, between the engine torque and the clutch torque.

2. The next-to-the-last selected value of the engagement point, asutilized by the control unit, was that shown at 714 in the coordinatesystem of FIG. 11. Such value was stored and was utilized, at leasttemporarily, by the control unit as a value denoting the engagementpoint. The value 714 is the last value which was utilized by the controlunit without effecting a change in the sign of the difference betweenthe engine torque and the clutch torque.

3. There is ascertained a median value between the two last ascertainedvalues (714, 715), and the thus ascertained median value is stored andutilized, at least temporarily, as that value of the engagement pointwhich is being utilized by the control unit. It will be seen that themedian value (714+715)/2 is obtained by utilizing the value (714) whichwas the last value that did not cause a change (s_(v)) of the sign ofthe difference between the engine torque and the desired clutch torque,and the value (715) which was the first value to cause such a change(S_(N)) of the sign.

4. An interpolation is carried out between the two last determinedvalues (714 and 715) of the engagement point, and the thus obtainedvalue is stored to be utilized, at least temporarily, by the controlunit as a value denoting the engagement point. The interpolated value isobtained on the basis of that utilized value at which the differencebetween the engine torque and the clutch torque did not indicate achange of sign (for the last time), and on the basis of that utilizedvalue (715) of the engagement point which, for the first time, indicateda change of the sign. The departures of the engine torque at Gp=714 orat Gp=715 from the desired clutch torque (of, for example, 6 Nm) can beconsidered as weighting factors.

The interpolation can be linear, square (second degree) or in accordancewith another predeterminable or preselectable function.

Once the engagement point has been ascertained and the at leasttemporarily utilized value of the engagement point has been stored, thedesired clutch torque is reduced at least substantially to zero prior toa renewed actuation of the clutch for a further adaptation of theengagement point or due to a changed condition of the motor vehicle.

During the individual time phases, the engine torque can be processed toassume an average value and the averaged value of the engine torque canbe compared with the desired clutch torque.

The length of the steps during incrementing or decrementing in thecourse of changing the engagement point (which is being utilized by thecontrol unit) between individual time intervals can be fixed, forexample to values in the range of between 0.02 mm to 1 mm. However, itis also possible that the increment/decrement depends from theascertained value of the engine torque. For example, the engine torquerange can be divided or broken up into discrete partial ranges, and adifferent increment/decrement can be selected for each such partialrange. This can be of advantage because one can utilize largerincrements/decrements when the values of the engine torque arerelatively small and one can use smaller increments/decrements when thevalue of the engine torque is higher. For example, this renders itpossible to achieve the desirable and advantageous result that thenumber of steps can be minimized in connection with a determination ofthe engagement point. It is also possible to make the length of thesteps or the value of an increment/decrement dependent upon thedeparture of the ascertained engine torque from the desired clutchtorque. For example, the length of the steps can bear a functionalrelationship with, such as being a percentage of, the departure.

FIG. 12 illustrates a different embodiment of the invention wherein theengagement point is ascertained by linear interpolation between theengagement point value M_(V) before and the engagement point value M_(N)after, i.e, at opposite sides of, the actual engagement point Gp. Thevalues M_(V) and M_(N) were ascertained by resorting to stepwiseincrementing/decrementing, as discussed with reference to thedescription of FIG. 11. The value M_(V) corresponds to that value of theengine torque, as shown by the curve 703 in FIG. 11, which was detectedprior to reaching the desired clutch torque M_(Ksoll) (curve 701 in FIG.11), and the value M_(N) corresponds to that value of the engine torquewhich was detected subsequent to reaching (by the engine torque) orsurpassing of the desired clutch torque M_(Ksoll). The desired clutchtorque M_(Ksoll) serves as a sampling torque which is being applied inorder to detect the reaction of the engine torque.

A linear interpolation (as indicated in FIG. 12 by a straight-line curve710) takes place between the values M_(N) and M_(V). The engagementpoint value or engagement value s_(V) is available at the torque valueM_(V), and the engagement point value or engagement value s_(N) isavailable at the torque value M_(N). The times t_(V) and t_(N) areutilized as auxiliary points for the purposes of illustration andcalculation. The instant t_(V) corresponds to the instant t₆, and theinstant t_(N) corresponds to the instant t₇.

The following linear equations are valid for the values M_(V) and M_(N)of the engine torque:

    M.sub.V =a*s.sub.V +b

    M.sub.N =a*s.sub.N +b

wherein the parameters M_(N), M_(V), s_(N) and s_(V) can be ascertainedby referring to FIG. 12. The values M_(N) and M_(V) correspond to thevalues of the engine torque prior and subsequent to reaching of thepredetermined desired clutch torque M_(Ksoll), and the parameters s_(N)and s_(V) denote set clutch positions s prior and subsequent to reachingof the predetermined desired clutch torque M_(Ksoll).

The following equations apply for the summands and factors a, b:##EQU1##

The following equation is valid for the engagement point Gp which isascertained by linear interpolation, with the values of M_(N), M_(V),s_(N), s_(V) and the sampling torque M_(Ksoll) : ##EQU2##

The value of the engagement point which is being utilized by the controlunit can be adapted in accordance with such value Gp of the engagementpoint.

By resorting to linear interpolation, the engagement point can beadapted with a higher degree of accuracy or, alternatively, by resortingto the above outlined procedure involving an incremental or decrementaladaptation of the engagement point, one can realize a more rapidcarrying out of an adaptation. For example, by resorting to aninterpolation of the engagement point Gp, the length of the steps duringincrementing/decrementing can be increased and one can still achieve arelatively high degree of accuracy.

FIGS. 13, 13a and 14 respectively show flow charts 800, 810 and 850denoting additional progresses of the novel determination and/oradaptation of the engagement point.

Step 801 in the flow chart 800 of FIG. 13 denotes the start of adetermination of the engagement point. At step 802, the torquetransmitting system (3) is set to a preselectable engagement position.Such position can be a preselectable position, such as an engagementpoint which has been selected in advance, or another preselectedposition. Next, at step 803, an averaging is performed of the detectedengine torque for a preselected interval of time Δt, and the resultingengine torque is stored as a comparison torque. At such time, the clutchis set basically not to transmit any torque. At step 804, the engagedcondition of the clutch is changed by a value Δs, for example toward theengaged or closed position starting from a previously selected value.For example, one can select a value Δs of 0.2 mm. At step 805, anaveraging is performed, for a time interval Δt, of the engine torquewhich has been detected or ascertained in such position, and theresulting or averaged engine torque is stored as a reference torque.Next, at step 806, a difference between the reference torque and thecomparison torque is determined, and such difference is compared with apreselectable value WERT. If the difference exceeds WERT, the systemproceeds to step 807, to ascertain the engagement point Gp from thearithmetic median of the last two positions of the clutch or of theactuating means therefor, and step 808 denotes a completion of thedetermination of the engagement point within the particular cycle.Alternatively, if the difference at step 806 does not exceed WERT, thesystem loops back and the position of the clutch or of the actuatingmeans therefor is altered at step 804, and the reference torque isdetermined anew, as indicated by at step 805.

Step 811 in the flow chart 810 of FIG. 13a denotes the initiation of adetermination of the engagement point. At step 812 of FIG. 13a thetorque transmitting system (such as 3) is set to a preselectableposition of engagement. This position can be a preselectable position,such as a previously determined engagement point, or another preselectedposition. Next, at step 813 of FIG. 13a, the engine torque which hasbeen determined at such time is averaged during a preselectable intervalΔt, and the resulting engine torque is stored as a comparison torque. Atsuch time, the clutch transmits a small torque or no torque at all. Atstep 814 the condition of the clutch is altered toward the engagedposition by the value WERT which is added to the value denoting theengagement point. Next, at step 815 the engine torque which has beendetected or otherwise ascertained at such time is averaged for apreselectable interval of time Δt, and the resulting engine torque isstored as a reference torque. At step 816, a difference between thereference torque and the comparison torque is determined, and suchdifference is compared with a preselectable value WERT. If thedifference exceeds WERT, the engagement point Gp is ascertained (step818) from the arithmetic median of the last two positions of the clutchor of the actuating means before the determination of the engagementpoint is terminated at step 819. Alternatively, if the difference atstep 816 does not exceed the value WERT, the engagement condition of theclutch is altered by an amount Δt, as indicated at step 817; forexample, it is shifted from the previous setting toward a more engagedcondition. For example, the value of Δt can be in the range of 0.2 mm.The system then proceeds to the next step (step 815), where thereference torque is determined anew, and at step 816 the differencebetween the reference torque and the comparison torque is compared withthe value of WERT.

Step 851 in the flow chart 850 of FIG. 14, indicates the initiation of adetermination of the engagement point. At step 852 the torquetransmitting system, such as the clutch 3, is set to a preselectablecondition of engagement. This condition can be a preselectable position,such as a previously determined engagement point, or another preselectedposition. Next, at step 853 the engine torque, which has been detectedat such time, is averaged for a preselectable time interval Δt and theresulting engine torque is stored as a comparison torque. At such time,the clutch transmits a minimal torque or no torque at all. At step 854the engagement of the clutch is changed by a value As, such as forexample starting from the previously selected value. For example, thevalue of Δs can be about 0.2 mm. Next, at step 855 the engine torquewhich has been detected or otherwise ascertained at such time isaveraged for a selectable time interval Δt, and the resulting torque isstored as reference torque. The system then proceeds to step 856 wherethe difference between the reference torque and the comparison torque isfirst established, and such difference is thereupon compared with apreselectable value WERT. If the difference exceeds the value of WERT(step 857), the engagement point Gp is ascertained from the arithmeticmedian of the two last positions of the clutch or from the last twopositions of the adjusting means for the clutch. The determination ofthe engagement point during the respective cycle is thereuponterminated, as indicated at step 858. Alternatively, if the differenceat step 856 does not exceed the value of WERT, the system loops back tostep 854 where the position of the clutch or of the actuating meanstherefor is altered, and the reference torque is determined anew, asindicated at step 855.

As already described above, by calculating starting from the engagementpoint which is being actually utilized by the control unit, one canselect or apply a sampling torque such as the desired clutch torqueM_(Ksoll) and thereupon detect the reaction of the engine torque as anindication of the transmissible torque and hence of the engagementpoint.

Such sampling torque is selected to match a preselectable value WERT sothat the reaction of the engine torque assumes a readily achievablevalue. Furthermore, the reaction of the engine torque to the samplingtorque should not be too pronounced. The procedure of determining theengagement point can be interrupted and a new sampling torque can bedetermined if the reaction of the engine torque to the sampling torqueexceeds a predeterminable threshold value. Thereupon, one can select anew sampling torque by taking into consideration the preceding samplingtorque and the raised engine torque.

The above can also be desirable when one selects a creeping operation,for example, when the start of the creeping operation is too pronouncedor takes place with an excessive torque because the real engagementpoint deviates from the engagement point which is being considered bythe control unit. For the sake of safety, it is desirable to furtherdisengage the clutch at least slightly when the torque reaction is toopronounced due to the selection of a relatively small creeping torque.In this context, a creeping operation is intended to denote a partialclosing of the clutch so that the vehicle can proceed to creep, slowly,while the gas pedal is not depressed, while the brake is not actuated,while the engine is running, and while the transmission has been shiftedinto an active (other than neutral) gear ratio.

The relied upon parameters and values can be detected by resorting tosensors or, for example, by way of data transmission from anotherelectronic unit or from a data bus such as a CAN-bus.

An adaptation of the engagement point is desirable in order tocompensate for or to balance thermally induced and/or wear-inducedshifting of the characteristic curve of the clutch (i.e., of the torquetransmitting system). For example, the adaptation of the engagementpoint can be carried out while the vehicle is at a standstill. Thefollowing conditions can be satisfied in order to initiate an adaptationof the engagement point:

idling switch: ON

main brake: ON

transmission RPM: 0 1/min!

desired clutch torque: 0 Nm!

the clutch temperature, as calculated by resorting to a temperaturemodel, should be uncritical, preferably below a threshold temperature offor example 300° C. The present invention further encompasses theinvention disclosed in the earlier-filed German application DE 19602006the disclosure of which is intended to be incorporated herein byreference.

The adaptation of the engagement point generates a cyclical samplingsignal or a sampling torque which is transmitted by the clutch and has aduration of, for example, 10 to 30 seconds. During the sampling cycles,the clutch is first fully disengaged or opened and is thereupon engagedfor an interval of 1 to 10 seconds to transmit a desired torque of 3 to20 Nm. The signal which denotes the engine torque is being detectedfirst while the clutch is disengaged and thereupon for an interval of 1to 10 seconds while the clutch is engaged, and the thus obtained signalsdenoting the engine torque can be thereupon averaged. If the differencebetween the two averaged values exceeds the preselected clutch torque,one adapts the short-lasting engagement point. The actual value of theincrement is a linear function of the difference between the increasesof the engine torque and the clutch torque. It amounts maximally to±0.01 to 2.0 mm.

If, at the time of evaluation of the balance of the clutch torque andthe engine torque, the last snifting step has been completed not morethan 5 to 600 seconds before, one also adapts the long-range engagementpoint. The increment which is being utilized for such purpose is smallerthan that for the short-lasting value of the engagement point by afactor of 1.1 to 20.

In this manner, the control unit can store for example two engagementpoint values each of which can be put to use.

The long-range engagement point value denotes, as a rule, theirreversible long-range changes of the engagement point, for examplethose which are attributable to wear upon or setting of the clutch orits diaphragm spring. The stored short-range engagement point isindicative, as a rule, of reversible short-lasting changes of theengagement point, for example, those which are attributable totemperature changes of the fluid column within the hydraulic system ofthe actuating means for the clutch, as indicated by the conduit 9 inFIG. 1.

If a snifting operation is being carried out, such as an equalization ofvolumes in the fluid-containing connection of the actuating means, thecontrol unit shifts from the stored short-lasting engagement point tothe stored long-range engagement point because, as, a rule, anequalization of volumes normally effects a shifting to the storedlong-range engagement point. The short-lasting stored value can bealtered thereafter as a result of reversible changes.

The operating point of a vehicle having an apparatus for actuation orselection or operation of an automated torque transmitting system, suchas for example a clutch, is a condition of the vehicle in the presenceof parameters. The operating point is defined by the parameters of thevehicle, such as for example, the shifting of the transmission into agiven gear ratio, an actuated brake, an engine RPM, a vehicle speed, atransmission RPM, the absence of a change of the engine torque, thenon-existence of an intent to shift the transmission into a differentgear ratio (i.e., non-actuation of the gear shifting lever), the absenceof depression of the gas pedal or of a value of gas pedal actuation, theexistence of acceleration, the driving in forward or reverse, a shiftingoperation or a driving condition while the vehicle speed remainsunchanged, or an increase or reduction of the speed of the vehicle. Adetection or an adaptation of a value of the engagement point can takeplace as a function of the values of such parameters of the vehicle.

The claims which are filed with this patent application are merelyproposed formulations without prejudicing the acquisition of broaderpatent protection. Applicant and its assignee reserve the right to claimadditional features such as those which, heretofore, are disclosed onlyin the specification and/or in the drawings.

The dependencies which are pointed out in dependent claims areindicative of further features of the subject matter recited in thereferred to claim or claims; such further features are intended to beprotected jointly with the features recited in the parent claim orclaims as well as independently.

In other words, the features which are recited in the dependent claimsare considered to constitute, or can constitute, inventions which are orwhich can be independent from the invention(s) recited in the parentclaim or claims.

Furthermore, the invention is not limited to those embodiments which aredescribed in the specification and/or illustrated in the drawings. Thus,the language of the claims is intended to further embrace numerousadditional changes and modifications, for example, all those which canbe arrived at by combining and/or modifying the illustrated and/ordescribed features in a number of ways and/or by combining theillustrated and/or described features with those which are recited inthe claims. This is considered to cover various component parts,combinations of parts, the methods and method steps as well as theprocedures of making, testing and/or otherwise treating or processingsuch parts and the combinations thereof.

I claim:
 1. A system for automatically regulating the transmission oftorque in a torque transmitting system, such as a clutch, by determiningan engagement point at which said clutch begins to transmit torque, saidsystem comprising:means for selecting a clutch torque to be a firstpredetermined clutch torque, which can be ascertained based on a storedvalue of an operating point and a characteristic curve of the clutch;means for measuring values of a parameter representing engine torque ina first phase, such values being optionally averaged; means forselecting the clutch torque to be a second predetermined clutch torquein a further phase; means for measuring values of a parameterrepresenting engine torque in said further phase, such values beingoptionally averaged; means for comparing the first and second clutchtorques and the parameter values in the first and second phasesrepresenting engine torque; means for determining whether a differencebetween said engine torques and said clutch torques exceeds apreselected limit value; means for altering a stored value of theengagement point in dependence on the difference between said enginetorques and said clutch torques.
 2. The system of claim 1, wherein theengagement point of the torque transmitting system is capable of beingadapted, at least at one operating point, in that a storable value ofthe engagement point which is utilized by the control unit is adapted toat least approximate, an actual physical value of the engagement point.3. The system of claim 2, wherein the value of the physical engagementpoint, is ascertainable or deducible on the basis of measurements orcalculations.
 4. The system of claim 3, wherein the position ofengagement is identified by the control unit as the engagement point andthe value of the thus ascertained engagement position is stored as thevalue of the engagement point.
 5. The system of claim 4, wherein thevalue which is stored as the engagement point originates from at leastone value which is ascertained as the engagement point.
 6. The system ofclaim 4, wherein the value which is stored as the engagement point isdeterminable from at least one value of a transmissible clutch torque atat least one predeterminable engagement position of the torquetransmitting system.
 7. The system of claim 4, wherein the value of aclutch torque transmissible by the torque transmitting system or adifference of such values is ascertainable from at least one value of anengine torque or a difference between the values of engine torque. 8.The system of claim 1, wherein the engagement point is adapted on thebasis of a planned adjustment of the torque transmitting system and adetermination of values in several steps.
 9. The system of claim 1,wherein, in the course of at least one of the selected or completedsteps, a measured value is used which at least approximately denotes theengine torque.
 10. The system of claim 1, wherein, in the course of atleast one of the selected or completed steps, one carries out anadjustment of the position of the clutch with a preselectable desiredclutch torque, the position of the clutch being ascertained with thepredeterminable desired clutch torque by means of a storedcharacteristic curve of the clutch and of the stored value of theengagement point.
 11. The system of claim 1, wherein, during at leasttwo of the selected or completed steps, measurement values are storedwhich at least represent the engine torque and in that, within at leastone other step a position of the clutch with a preselectable desiredclutch torque is adjusted and the desired clutch torque is ascertainedon the basis of a stored characteristic curve of the clutch and thestored value of the operating point.
 12. The system of claim 1, whereinat least two measurement values or magnitudes are ascertained indifferently selected positions of the clutch or at a differentpreselectable desired clutch torque.
 13. The system of claim 11, whereinthe measurement values or magnitudes of both measurement intervals areobtained or ascertained in different positions of the clutch or atdifferent clutch torques.
 14. The system of claim 1, wherein averagevalues of data are used for each measurement interval by resorting todata, such as measured values or magnitudes.
 15. The system of claim 1,wherein the engagement point of the torque transmitting system isdetermined on the basis of at least one measured value of a parameterdenoting the engine torque at least at one selected clutch position orat a desired clutch torque.
 16. The system of claim 13, wherein theascertained value of the engagement point is compared with a storedvalue of an engagement point.
 17. The system of claim 16, wherein theascertained value of the engagement point is compared with a storedvalue of an engagement point and the stored value is altered in responseto the detection of a determinable difference between such values. 18.The system of claim 17, wherein the stored value is altered at least insuch a way that the stored value at least approximates the ascertainedvalue.
 19. The system of claim 17, wherein the stored value is alteredat least in such a way that the stored value is caused to approach theascertained value at least in a stepwise fashion with steps of apredeterminable length.
 20. The system of claim 17, wherein the storedvalue approaches the ascertained value at least in a stepwise fashionwith steps of predeterminable length, the length of the steps beingpredeterminable or being in a functional relationship with thedifference.
 21. The system of claim 1, wherein difference between themeasured values of a parameter denoting the engine torque areascertained on the basis of values, such as measured values, of a valuedenoting the engine torque and on the basis of clutch torques, and adifference between the values of the clutch torques is ascertained, andthat such differences are compared, and at least one stored value of theengagement point is altered in the event of lack of equality or independency upon the departure in response to detection of a lack ofequality between the aforementioned differences or when the lack ofequality exceeds a predeterminable value.
 22. The system of claim 21,wherein, in the event of inequality or a departure of equality beyond apredeterminable tolerance between the difference of values denoting theengine torque and the difference denoting the clutch torque, anadaptation of the engagement point takes place incrementally ordecrementally.
 23. The system of claim 1, wherein the measurement valuesor magnitudes for the determination of the parameter denoting an enginetorque or a difference of the magnitudes denoting the engine torque areascertained on the basis of signals which are characteristic of theactual load upon the engine, including, the engine torque, the engineRPM, signal from the load lever, position of the throttle valve, timingof the ignition, ignition angle, pressure in the suction manifold or thetiming of fuel injection.
 24. The system of claim 1, wherein theselection of the clutch torque by the control unit, at least in oneoperating point, is carried out in accordance with the engagement pointto correspond to a predeterminable desired clutch torque at a clutchsetting or at a selected clutch torque in such a way that, during afirst phase measurement values are taken up denoting a value whichrepresents the engine torque, that such values are averaged if desiredor necessary, that such values of the engine torque are thereuponcompared with the selected desired clutch torque and, if the departureis greater than a preselectable value, the value of the engagement pointis incremented or decremented at least in a stepwise fashion and,thereafter, the procedure is repeated in response to detection of anincremented or decremented value until the departure is smaller than thepreselectable value.
 25. The structure of claim 24, wherein the lengthof steps of stepwise incrementing or decrementing the value of theengagement point has a predeterminable value or is dependent on thedeparture between said engine torque values and said clutch torquevalues.
 26. The system of claim 1, wherein when the clutch is disengagedand the transmissible torque is disappearing, the engine torque,thereupon the clutch torque are ascertained, such as the transmissibleclutch torque, is set to the value of the engagement point plus adesired or required clutch torque, and the engine torque is ascertainedand, if the value of a predeterminable difference between the enginetorque and the clutch torque is exceeded, the value of the engagementpoint is increased stepwise and the engine torque is ascertained everytime thereafter until the difference between the engine torque and theclutch torque is smaller than the predeterminable difference, and thethen existing value of the engagement point is stored.
 27. The system ofclaim 26, wherein the stepwise incrementing or decrementing of the valueof the engagement point is carried out until the engine torque which hasbeen ascertained during two successive steps is once less and once morethan the selected clutch torque, and one of the two last values of theengagement point is stored.
 28. The system of claim 27, wherein thestepwise incrementing or decrementing of the value of the engagementpoint is carried out until the ascertained engine torque during twosuccessive steps is once smaller and once larger than the selectedclutch torque, the physical value of the engagement point beingdetermined at least by way of the last two values of the engagementpoint.
 29. The system of claim 27, wherein the physical value of theengagement point is ascertained on the basis of at least two values,such as the two last values of the engagement point, by establishing anaverage value.
 30. The system of claim 29, wherein value of theengagement point is ascertained on the basis of at least two values,such as the last two ascertained values of the engagement point, byinterpolation.
 31. The system of claim 30, wherein the value of theengagement point is ascertained by a linear or a nonlinear, such as asquare, cubic and other, interpolation.
 32. The system of claim 1,wherein during ascertainment or adaptation of the engagement point,negative torque are selected as clutch torque, the negative torque beingdefined in that, starting from the engagement point, the clutch is setto a position in a direction toward disengagement of the clutch.
 33. Thesystem of claim 1, wherein during ascertainment or adaptation of theengagement point, clutch positions are selected which are disposedbetween the fully opened clutch position and the engagement point. 34.The system of claim 32, wherein following an adjustment to a negativetorque or to a clutch position between a fully open position and theengagement point, there follows the ascertainment of a value whichdenotes the engine torque and, when a change of the value denoting theengine torque relative to an adjustment of the clutch position to theengagement point occurs, the value of the engagement point is adapted.35. The system of claim 1, wherein, in the event of a selection of adesired clutch torque as a sampling torque, the reaction of the enginetorque is detected and, when the engine torque exceeds a preselectablethreshold, the clutch is disengaged and the sampling torque is reduced.36. In a motor vehicle, the combination of a driving unit, atransmission, a torque transmitting system, such as a friction clutch,and a central control unit which is connected in a signal-transmittingmanner with at least one sensor and which controls the torque adapted tobe transmitted by the torque transmitting system in dependency upon theoperating point or as a function of time, the operating point whichdenotes the position of engagement at a time when the transmission oftorque begins is adapted in such a way that at least one set of datadenoting the engagement point and being utilized by the control unit andbeing stored in at least one memory is caused to at least approximate,at least in a stepwise fashion, the at least one physical engagementpoint.
 37. In a motor vehicle, the combination of a driving unit, atransmission, an automated torque transmitting system, such as afriction clutch, a central control unit as well as at least oneadjusting member which is actuatable by the control unit which serves toselect the torque to be transmitted by the torque transmitting system,the torque to be transmitted by the torque transmitting system beingselectable within a range between a fully disengaged position in whichthe transmissible torque equals zero and a fully engaged position inwhich the transmissible torque assumes a maximum value, wherein thephysically existing engagement point which characterizes the position ofengagement at the onset of torque transmission, is compared on the basisof a planned regulation by the control unit as a function of time or independency upon the operating point with at least one set of datapertaining to the engagement point and being stored in a memory, and theset of data is adapted, at least stepwise, in the event of departures ofthe physical engagement point from the set of data denoting theengagement point.
 38. In a motor vehicle, the combination of a drivingunit, a transmission, an automated torque transmitting system, such as afriction clutch, a central control unit as well as at least oneadjusting member which is actuatable by the control unit and serves toselect the torque to be transmitted by the torque transmitting unit, thetorque to be transmitted by the torque transmitting system beingselectable within a range between a fully disengaged position in whichthe transmissible torque equals zero and a fully engaged position inwhich the transmissible torque assumes a maximum value, wherein theengagement point is adapted in accordance with at least one of thefollowing criteria:an adaptation of the engagement point on the basis oflong-range variations of the engagement point as a result of developingchanges in the power train or in the torque transmitting system; anadaptation of the engagement point on the basis of changes of theengagement point as a result of short-lasting changes in the power trainor in the torque transmitting system.
 39. A method of automaticallyregulating the transmission of torque in a torque transmitting system,such as a clutch, by determining an engagement point at which saidclutch begins to transmit torque, the method comprising the followingsteps:(a) the clutch torque is selected for a preselectable position ofthe clutch or at a preselectable desired clutch torque; (b) in a firstphase measurement values are taken of a parameter which denotes theengine torque, such values being adapted to be averaged if desired ornecessary; (c) a predeterminable position of the clutch or apredeterminable desired clutch torque is selected in a second phase; (d)measurement values denoting a parameter which is indicative of theengine torque are ascertained and, if desired or necessary, averaged ina third phase; (e) a comparison is carried out at least between thevalues referred to in the steps (a) and (c) and denoting the enginetorque, and the values of the desired clutch torque; and (f) themonitored engagement point is altered in dependency upon the abovesteps.
 40. The method of claim 39 wherein during ascertainment oradaptation of the engagement point, "negative torques" are selected asclutch torque, the "negative torques" being defined in that, startingfrom the engagement point, the clutch is set to a position in adirection toward disengagement of the clutch.
 41. The method of claim 39wherein during ascertainment or adaptation of the engagement point,clutch positions are selected which are disposed between the fullyopened clutch position and the engagement point.
 42. The method of claim39 wherein, in the event of a selection of a desired clutch torque as asampling torque, the reaction of the engine torque is detected and, whenthe engine torque exceeds a preselectable threshold, the clutch isdisengaged and the sampling torque is reduced.
 43. The method of claim39 wherein, in accordance with said method the value of at least oneengagement point which is stored in at least one memory is caused toapproximate a physically existing engagement point which characterizesthe position of engagement of the clutch at the instant when thetransmission of torque begins, the approximation taking place as aresult of an adjustment of the torque transmitting system as a functionof time and/or as a function of the operating point.
 44. The method ofclaim 40, wherein following an adjustment to a negative torque or to aclutch position between a fully open position and the engagement point,there follows the ascertainment of a value which denotes the enginetorque and, when a change of the value denoting the engine torquerelative to an adjustment of the clutch position to the engagement pointoccurs, the value of the engagement point is adapted.
 45. A method ofautomatically regulating the transmission of torque in a torquetransmitting system, such as a clutch, by determining an engagementpoint at which said clutch begins to transmit torque, the methodcomprising the following steps:(a) the clutch torque is selected in apreselectable ascertained clutch position or at a predeterminableselected desired clutch torque, which can be ascertained on the basis ofthe stored value of the operating point and of a characteristic curve ofthe clutch, (b) measurement values of a parameter representing a clutchtorque are ascertained in a preselectable time window, such values beingaveraged if necessary or desired, (c) a further predeterminable desiredclutch torque is selected in a further phase, (d) measurement values ofa parameter denoting the engine torque are ascertained in a furtherphase and are averaged, if necessary or desired, (e) a comparison iscarried out at least between those values of the steps (b) and (d) whichdenote the engine torque and the values denoting the desired clutchtorques of the steps (a) and (c), (f) an evaluation is made whether ornot a difference between at least one engine torque and at least onedesired clutch torque exceeds a preselectable limit value, and (g) thestored value of the engagement point is altered, if necessary, independency upon the comparison or in dependency upon the extent of thedeparture.
 46. A system for automatically regulating the transmission oftorque in a torque transmitting system, such as a clutch, by determiningan engagement point at which said clutch begins to transmit torque, saidsystem comprising:means for selecting a clutch torque to be a firstpredetermined clutch torque, which can be ascertained based on a storedvalue of an operating point and a characteristic curve of the clutch;means for measuring values of a parameter representing engine torque ina first phase, such values being optionally averaged; means forselecting the clutch torque to be a second predetermined clutch torquein a further phase; means for measuring values of a parameterrepresenting engine torque in said further phase, such values beingoptionally averaged; means for comparing the first and second clutchtorques and the parameter values in the first and second phasesrepresenting engine torque; means for altering the engagement point byincrementing/decrementing said engagement point and storing said alteredengagement point and utilizing said system to iteratively alter saidengagement point if a difference between said first and second clutchtorques and the parameter values in the first and second phases exceedsa predetermined limit.
 47. A method of automatically regulating thetransmission of torque in a torque transmitting system, such as aclutch, by determining an engagement point at which said clutch beginsto transmit torque, the method comprising the following steps:(a) theclutch torque is selected in a preselectable clutch position or at apreselectable clutch torque; (b) the measurement values of a parameterdenoting the engine torque are determined, and averaged if necessary ordesired, in a first phase; (c) a predeterminable clutch position or apredeterminable desired clutch torque is set in a second phase; (d)measured values of a parameter denoting the engine torque areascertained and, if necessary or desired, averaged in a third phase; (e)and a comparison is carried out between those values of the steps (a)and (c) which denote the values of the engine torque and the values ofthe desired clutch torques, and (f) the engagement point isincrementally/decrementally altered and stored, and the procedure iscarried out anew from the step (a), when the comparison indicates adifference which departs from a predeterminable tolerance.
 48. A systemfor automatically regulating the transmission of torque in a torquetransmitting system, such as a clutch, by determining an engagementpoint at which said clutch begins to transmit torque, said systemcomprising:means for selecting a clutch torque to be a firstpredetermined clutch torque, which can be ascertained based on a storedvalue of an operating point and a characteristic curve of the clutch;means for measuring values of a parameter representing engine torque ina first phase, such values being optionally averaged; means forselecting the clutch torque to be a second predetermined clutch torquein a further phase; means for measuring values of a parameterrepresenting engine torque in said further phase, such values beingoptionally averaged; means for comparing the first and second clutchtorques and the parameter values in the first and second phasesrepresenting engine torque; means for altering the engagement point byincrementing/decrementing said engagement point and storing said alteredengagement point and utilizing said system to iteratively alter saidengagement point using said first clutch torque and said first phaseparameter values and a new second clutch torque and a new second phaseparameter value if a difference between said first and second clutchtorques and the parameter values in the first and second phases exceedsa predetermined limit.
 49. A method of automatically regulating thetransmission of torque in a torque transmitting system, such as aclutch, by determining an engagement point at which said clutch beginsto transmit torque, the method comprising the following steps:(a) theclutch torque is selected in a preselectable position of the clutch orat least at one preselectable desired clutch torque; (b) measurementvalues of a parameter denoting the engine torque are determined and, ifnecessary or desired, averaged in a first phase; (c) a predeterminableposition of the clutch or a predeterminable desired clutch torque is setin a second phase; (d) measurement values of a parameter denoting theengine torque are ascertained and, if necessary or desired, averaged ina third phase; (e) and a comparison is carried out between those valuesof the steps (a) and (c) which denote the engine torque and the valuesof the desired clutch torque, and (f) the engagement point is alteredincrementally/decrementally and is stored, and the procedure is carriedout anew from the step (c) on, the data of the points (a) and (b) beingstill utilizable, when the difference departs from a predeterminabletolerance.
 50. A method of automatically regulating the transmission oftorque in a torque transmitting system, such as a clutch, by determiningan engagement point at which said clutch begins to transmit torque, themethod comprising the following steps: ascertaining on the basis ofvalues, such as measured values, of a value denoting the engine torqueand on the basis of clutch torques, and a difference between the valuesof the clutch torques is ascertained, and that such differences arecompared, and at least one stored value of the engagement point isaltered in the event of lack of equality or in dependency upon thedeparture in response to detection of a lack of equality between theaforementioned differences or when the lack of equality exceeds apredeterminable value.
 51. The method of claim 50, wherein, in the eventof inequality or a departure of equality beyond a predeterminabletolerance between the difference of values denoting the engine torqueand the difference denoting the clutch torque, an adaptation of theengagement point takes place incrementally or decrementally.
 52. Amethod of automatically regulating the transmission of torque in atorque transmitting system, such as a clutch, by determining anengagement point at which said clutch begins to transmit torque, themethod comprising the following steps: the selection of the clutchtorque by the control unit, at least in one operating point, is carriedout in accordance with the engagement point to correspond to apredeterminable desired clutch torque at a clutch setting or at aselected clutch torque in such a way that, during a first phasemeasurement values are taken up denoting a value which represents theengine torque, that such values are averaged if desired or necessary,that such values of the engine torque are thereupon compared with theselected desired clutch torque and, if the departure is greater than apreselectable value, the value of the engagement point is incremented ordecremented at least in a stepwise fashion and, thereafter, theprocedure is repeated in response to detection of an incremented ordecremented value until the departure is smaller than the preselectablevalue.
 53. The method of claim 52, wherein the length of steps ofstepwise incrementing or decrementing the value of the engagement pointhas a predeterminable value or is dependent on the departure betweensaid engine torque values and said clutch torque values.
 54. A method ofautomatically regulating the transmission of torque in a torquetransmitting system, such as a clutch, by determining an engagementpoint at which said clutch begins to transmit torque, the methodcomprising the following steps: wherein when the clutch is disengagedand the transmissible torque is disappearing, the engine torque,thereupon the clutch torque are ascertained, such as the transmissibleclutch torque, is set to the value of the engagement point plus adesired or required clutch torque, and the engine torque is ascertainedand, if the value of a predeterminable difference between the enginetorque and the clutch torque is exceeded, the value of the engagementpoint is increased stepwise and the engine torque is ascertained everytime thereafter until the difference between the engine torque and theclutch torque is smaller than the predeterminable difference, and thethen existing value of the engagement point is stored.
 55. The method ofclaim 54, wherein the stepwise incrementing or decrementing of the valueof the engagement point is carried out until the engine torque which hasbeen ascertained during two successive steps is once less and once morethan the selected clutch torque, and one of the two last values of theengagement point is stored.
 56. The method of claim 55, wherein thestepwise incrementing or decrementing of the value of the engagementpoint is carried out until the ascertained engine torque during twosuccessive steps is once smaller and once larger than the selectedclutch torque, the physical value of the engagement point beingdetermined at least by way of the last two values of the engagementpoint.
 57. The method of claim 55, wherein physical value of theengagement point is ascertained on the basis of at least two values,such as the two last values of the engagement point, by establishing anaverage value.
 58. The method of claim 55, wherein the physical value ofthe engagement point is ascertained on the basis of at least two values,such as the two last values of the engagement point, by way of linearregression.
 59. The method of claim 55, wherein the physical value ofthe engagement point is ascertained on the basis of at least two values,such as the two last values of the engagement point, by way of linearregression.
 60. The method of claim 57, wherein value of the engagementpoint is ascertained on the basis of at least two values, such as thelast two ascertained values of the engagement point, by interpolation.61. The method of claim 60, wherein the value of the engagement point isascertained by a linear or a nonlinear, such as a square, cubic andother, interpolation.
 62. The method of claim 43, wherein the adaptationof the engagement point takes place by resorting to a multiple-stepprocedure, a first step involving the determination of measured valuesand the determination of an averaged engine torque, a second stepinvolving a setting of a clutch torque, and a third step involving adetermination of measured values and a determination of an averagedengine torque and, based on a comparison of the averaged data pertainingto the engine torques with the data denoting the clutch torques, the setof data pertaining to the engagement point is caused to approach thephysical engagement point, a further step involving the setting of theoriginally prevailing clutch torque.
 63. A method of adapting theengagement point of a torque transmitting system in the power train of amotor vehicle with a control unit and an adjusting member and sensorsfor the determination of measured values, wherein the setting of theclutch at least at one operating point comprises at least one of thefollowing steps:(a) setting of a clutch position at which essentially notorque is being transmitted, (b) setting of a clutch position at which adesired clutch torque (M_(Ksoll)) is to be transmitted, (c)determination of measured values which denote the engine torque and/oron the basis of which the engine torque is ascertainable, (d) averagingthe measured values, (e) establishment of a difference between thevalues of the torque, such as averaged values of the torque, (f)comparing the values of the torques, such the values of averagedtorques, (g) incrementing/decrementing of the at least one stored valueof the engagement point.
 64. The method of claim 63, wherein, in atleast one operating point the adjustment of the clutch for the purposeof adapting the engagement point takes place in at least four steps, oneof these steps involving setting the position of the clutch at a valueat which a predetermined torque M_(K1) is to be transmitted, a furtherstep involving ascertaining within a time, window ΔT₁, at a constantposition of the clutch, measured values M_(Motor) which are thereuponaveraged or calculated to M_(M1) denoting the engine torque, a furtherstep involving the setting of a clutch position at which a predetermineddesired or expected clutch torque M_(K2) is to be capable of beingtransmitted, a further step involving ascertaining within a time windowΔT₂, at a constant position of the clutch, measured values M_(Motor) andthereupon averaging or calculating such measured values to M_(M2), and afurther step involving a comparison basically of the difference betweenthe average values M_(M2) -M_(M1) of the engine torque and thedifferences between the desired clutch torque values M_(K2) -M_(K1), thestored engagement point GP being incremented/decremented by a value ΔGPwhen the comparison reveals that M_(M2) -M_(M1) is larger/smaller thanM_(K2) -M_(K1) and the difference eventually exceeds a preselectablethreshold.
 65. The method of claim 63, wherein at least one operatingpoint is realized for the adaptation of the operating point while themotor vehicle is at a standstill, while the vehicle is in a gear, andwhile the brake is being applied.
 66. The method of claim 64, whereinthe time windows ΔT₁ and ΔT₂ are either identical or of differentduration, and at least one measured value being ascertained per timewindow.
 67. The method of claim 66, wherein the duration of the timewindows ΔT₁ and ΔT₂ is within the range of 0.1 second to 10 seconds, itbeing preferred to select a duration of 1 to 5 seconds, especiallybetween 1 and 3 seconds.
 68. The method of claim 43, wherein theadaptation is for a long-range or a short-lasting engagement point. 69.The method of claim 68, wherein the long-range engagement point isadapted on the basis of development of long-range changes in the entiretorque transmission system.
 70. The method of claim 68, wherein thelong-range engagement point is adapted at special operating points, suchas for example during a snifting stage.
 71. The method of claim 70,wherein the short-lasting engagement point is adapted in view ofshort-lasting reversible or irreversible changes in the entire torquetransmitting system.
 72. The method of claim 68, wherein the value ofthe increment or decrement of long-range adaptation is less than ormatches the value of the short-lasting adaptation.